The dilemma arises whatever the source of authority is supposed to be. Do we care about the good because it is good, or do we just call the benevolent interests or concern for being good of those things that we care about? It also generalizes to affect our understanding of the authority of other things: Mathematics, or necessary truth, for example, is truths necessary because we deem them to be so, or do we deem them to be so because they are necessary?
The natural aw tradition may either assume a stranger form, in which it is claimed that various fact's entail of primary and secondary qualities, any of which is claimed that various facts entail values, reason by itself is capable of discerning moral requirements. As in the ethics of Kant, these requirements are supposed binding on all human beings, regardless of their desires.
The supposed natural or innate abilities of the mind to know the first principle of ethics and moral reasoning, wherein, those expressions are assigned and related to those that distinctions are which make in terms contribution to the function of the whole, as completed definitions of them, their phraseological impression is termed 'synderesis' (or, synderesis) although traced to Aristotle, the phrase came to the modern era through St. Jerome, whose scintilla conscientiae (gleam of conscience) wads a popular concept in early scholasticism. Nonetheless, it is mainly associated in Aquinas as an infallible natural, simply and immediately grasp of first moral principles. Conscience, by contrast, is, more concerned with particular instances of right and wrong, and can be in error, under which the assertion that is taken as fundamental, at least for the purposes of the branch of enquiry in hand.
It is, nevertheless, the view interpreted within the particular states of law and morality especially associated with Aquinas and the subsequent scholastic tradition, showing for itself the enthusiasm for reform for its own sake. Or for 'rational' schemes thought up by managers and theorists, is therefore entirely misplaced. Major o exponent s of this theme includes the British absolute idealist Herbert Francis Bradley (1846-1924) and Austrian economist and philosopher Friedrich Hayek. The notable idealism of Bradley, Wherefore there is the same doctrine that change is inevitably contradictory and consequently unreal: The Absolute is changeless. A way of sympathizing a little with his idea is to reflect that any scientific explanation of change will proceed by finding an unchanging law operating, or an unchanging quantity conserved in the change, so that explanation of change always proceeds by finding that which is unchanged. The metaphysical problem of change is to shake off the idea that each moment is created afresh, and to obtain a conception of events or processes as having a genuinely historical reality, Really extended and unfolding in time, as opposed to being composites of discrete temporal atoms. A step toward this end may be to see time itself not as an infinite container within which discrete events are located, but as a kind of logical construction from the flux of events. This relational view of time was advocated by Leibniz and a subject of the debate between him and Newton's Absolutist pupil, Clarke.
Generally, nature is an indefinitely mutable term, changing as our scientific conception of the world changes, and often best seen as signifying a contrast with something considered not part of nature. The term applies both to individual species (it is the nature of gold to be dense or of dogs to be friendly), and also to the natural world as a whole. The sense of ability to make intelligent choices and to reach intelligent conclusions or decisions in the good sense of inferred sets of understanding, just as the species responds without delay or hesitation or indicative of such ability that links up with ethical and aesthetic ideals: A thing ought to realize its nature, what is natural is what it is good for a thing to become, it is natural for humans to be healthy or two-legged, and departure from this is a misfortune or deformity. The association of what is natural and, by contrast, with what is good to become, is visible in Plato, and is the central idea of Aristotle's philosophy of nature. Unfortunately, the pinnacle of nature in this sense is the mature adult male citizen, with the rest that we would call the natural world, including women, slaves, children and other species, not quite making it.
Nature in general can, however, function as a foil to any idea inasmuch as a source of ideals: In this sense fallen nature is contrasted with a supposed celestial realization of the 'forms'. The theory of 'forms' is probably the most characteristic, and most contested of the doctrines of Plato. In the background, i.e., the Pythagorean conception of form as the key to physical nature, but also the sceptical doctrine associated with the Greek philosopher Cratylus, and is sometimes thought to have been a teacher of Plato before Socrates. He is famous for capping the doctrine of Ephesus of Heraclitus, whereby the guiding idea of his philosophy was that of the logos, is capable of being heard or hearkened to by people, it unifies opposites, and it is somehow associated with fire, which is pre-eminent among the four elements that Heraclitus distinguishes: Fire, air (breath, the stuff of which souls composed), Earth, and water. Although he is principally remembered for the doctrine of the 'flux' of all things, and the famous statement that you cannot step into the same river twice, for new waters are ever flowing in upon you. The more extreme implication of the doctrine of flux, e.g., the impossibility of categorizing things truly, do not seem consistent with his general epistemology and views of meaning, and were to his follower Cratylus, although the proper conclusion of his views was that the flux cannot be captured in words. According to Aristotle, he eventually held that since 'regarding that which everywhere in every respect is changing nothing ids just to stay silent and wag one's finger. Plato's theory of forms can be seen in part as an action against the impasse to which Cratylus was driven.
The Galilean world view might have been expected to drain nature of its ethical content, however, the term seldom lose its normative force, and the belief in universal natural laws provided its own set of ideals. In the 18th century for example, a painter or writer could be praised as natural, where the qualities expected would include normal (universal) topics treated with simplicity, economy, regularity and harmony. Later on, nature becomes an equally potent emblem of irregularity, wildness, and fertile diversity, but also associated with progress of human history, its incurring definition that has been taken to fit many things as well as transformation, including ordinary human self-consciousness. Nature, being in contrast within integrated phenomenons’ may include (1) that which is deformed or grotesque or fails to achieve its proper form or function or just the statistically uncommon or unfamiliar, (2) the supernatural, or the world of gods and invisible agencies, (3) the world of rationality and unintelligence, conceived of as distinct from the biological and physical order, or the product of human intervention, and (5) related to that, the world of convention and artifice.
Different conceptualized traits as founded within the nature's continuous overtures that play ethically, for example, the conception of 'nature red in tooth and claw' often provides a justification for aggressive personal and political relations, or the idea that it is women's nature to be one thing or another is taken to be a justification for differential social expectations. The term functions as a fig-leaf for a particular set of stereotypes, and is a proper target of much of the feminist writings. Feminist epistemology has asked whether different ways of knowing for instance with different criteria of justification, and different emphases on logic and imagination, characterize male and female attempts to understand the world. Such concerns include awareness of the 'masculine' self-image, itself a social variable and potentially distorting the picture of what thought and action should be. Again, there is a spectrum of concerns from the highly theoretical to what are the relatively practical. In this latter area particular attention is given to the institutional biases that stand in the way of equal opportunities in science and other academic pursuits, or the ideologies that stand in the way of women seeing themselves as leading contributors to various disciplines. However, to more radical feminists such concerns merely exhibit women wanting for themselves the same power and rights over others that men have claimed, and failing to confront the real problem, which is how to live without such symmetrical powers and rights.
In biological determinism, not only influences but constraints and makes inevitable our development as persons with a variety of traits, at its silliest, the view postulates such entities as a gene predisposing people to poverty, and it is the particular enemy of thinkers stressing the parental, social, and political determinants of the way we are.
The philosophy of social science is more heavily intertwined with actual social science than in the case of other subjects such as physics or mathematics, since its question is centrally whether there can be such a thing as sociology. The idea of a 'science of man', devoted to uncovering scientific laws determining the basic dynamic s of human interactions was a cherished ideal of the Enlightenment and reached its heyday with the positivism of writers such as the French philosopher and social theorist Auguste Comte (1798-1957), and the historical materialism of Marx and his followers. Sceptics point out that what happens in society is determined by peoples' own ideas of what should happen, and like fashions those ideas change in unpredictable ways as self-consciousness is susceptible to change by any number of external event s: Unlike the solar system of celestial mechanics a society is not at all a closed system evolving in accordance with a purely internal dynamic, but constantly responsive to shocks from outside.
The sociological approach to human behaviour is based on the premise that all social behaviour has a biological basis, and seeks to understand that basis in terms of genetic encoding for features that are then selected for through evolutionary history. The philosophical problem is essentially one of methodology: Of finding criteria for identifying features that can usefully be explained in this way, and for finding criteria for assessing various genetic stories that might provide useful explanations.
Among the features that are proposed for this kind of explanation are such things as male dominance, male promiscuity versus female fidelity, propensities to sympathy and other emotions, and the limited altruism characteristic of human beings. The strategy has proved unnecessarily controversial, with proponents accused of ignoring the influence of environmental and social factors in moulding people's characteristics, e.g., at the limit of silliness, by postulating a 'gene for poverty', however, there is no need for the approach to committing such errors, since the feature explained psychobiological may be indexed to environment: For instance, it may be a propensity to develop some feature in some other environments (for even a propensity to develop propensities . . .) The main problem is to separate genuine explanation from speculative, just so stories which may or may not identify as really selective mechanisms.
Subsequently, in the 19th century attempts were made to base ethical reasoning on the presumed facts about evolution. The movement is particularly associated with the English philosopher of evolution Herbert Spencer (1820-1903). His first major work was the book Social Statics (1851), which promoted an extreme political libertarianism. The Principles of Psychology was published in 1855, and his very influential Education advocating natural development of intelligence, the creation of pleasurable interest, and the importance of science in the curriculum, appeared in 1861. His First Principles (1862) was followed over the succeeding years by volumes on the Principles of biology and psychology, sociology and ethics. Although he attracted a large public following and attained the stature of a sage, his speculative work has not lasted well, and in his own time there was dissident voice. T.H. Huxley said that Spencer's definition of a tragedy was a deduction killed by a fact. Writer and social prophet Thomas Carlyle (1795-1881) called him a perfect vacuum, and the American psychologist and philosopher William James (1842-1910) wondered why half of England wanted to bury him in Westminister Abbey, and talked of the 'hurdy-gurdy' monotony of him, his aggraded organized array of parts or elements forming or functioning as some units were in cohesion of the opening contributions of wholeness and the system proved inseparably unyieldingly.
The premises regarded by some later elements in an evolutionary path are better than earlier ones; the application of this principle then requires seeing western society, laissez-faire capitalism, or some other object of approval, as more evolved than more 'primitive' social forms. Neither the principle nor the applications command much respect. The version of evolutionary ethics called 'social Darwinism' emphasizes the struggle for natural selection, and drawn the conclusion that we should glorify such struggles, usually by enhancing competitive and aggressive relations between people in society or between societies themselves. More recently the relation between evolution and ethics has been re-thought in the light of biological discoveries concerning altruism and kin-selection.
In that, the study of the way in which a variety of higher mental functions may be adaptations applicable of a psychology of evolution, an outward appearance of something as distinguished from the substances of which it is made, as the conduct regulated by an external control as a custom or formal protocol of procedure may, perhaps, depicts the conventional convenience in having been such at some previous time the hardened notational system in having no definite or recognizable form in response to selection pressures on human populations through evolutionary time. Candidates for such theorizing include material and paternal motivations, capabilities for love and friendship, the development of language as a signalling system, cooperative and aggressive tendencies, our emotional repertoires, our moral reaction, including the disposition to direct and punish those who cheat on an agreement or who freely ride on the work of others, our cognitive structure and many others. Evolutionary psychology goes hand-in-hand with Neurophysiologic evidence about the underlying circuitry in the brain which subserves the psychological mechanisms it claims to identify.
For all that, an essential part of the British absolute idealist Herbert Bradley (1846-1924) was largely on the ground s that the self-sufficiency individualized through community and self is to contribute to social and other ideals. However, truth as formulated in language is always partial, and dependent upon categories that they are inadequate to the harmonious whole. Nevertheless, these self-contradictory elements somehow contribute to the harmonious whole, or Absolute, lying beyond categorization. Although absolute idealism maintains few adherents today, Bradley's general dissent from empiricism, his holism, and the brilliance and style of his writing continues to make him the most interesting of the late 19th century writers influenced by the German philosopher Friedrich Hegel (1770-1831).
Understandably, something less than the fragmented division that belonging of Bradley's case has a preference, voiced much earlier by the German philosopher, mathematician and polymath, Gottfried Leibniz (1646-1716), for categorical monadic properties over relations. He was particularly troubled by the relation between that which is known and the more that knows it. In philosophy, the Romantics took from the German philosopher and founder of critical philosophy Immanuel Kant (1724-1804) both the emphasis on free-will and the doctrine that reality is ultimately spiritual, with nature itself a mirror of the human soul. To fix upon one among alternatives as the one to be taken, Friedrich Schelling (1775-1854), who is now qualified to be or worthy of being chosen as a condition, position or state of importance is found of a basic underlying entity or form that he succeeds fully or in accordance with one's attributive state of prosperity, the notice in conveying completely the cruel essence of those who agree and disagrees its contention to 'be-all' and 'end-all' of essentiality. Nonetheless, the movement of more general to naturalized imperatives are nonetheless, simulating the movement that Romanticism drew on by the same intellectual and emotional resources as German idealism was increasingly culminating in the philosophy of Hegal (1770-1831) and of absolute idealism.
Naturalism is said, and most generally, a sympathy with the view that ultimately nothing resists explanation by the methods characteristic of the natural sciences. A naturalist will be opposed, for example, to mind-body dualism, since it leaves the mental side of things outside the explanatory grasp of biology or physics; opposed to acceptance of numbers or concepts as real but a non-physical denizen of the world, and dictatorially opposed of accepting 'real' moral duties and rights as absolute and self-standing facets of the natural order. A major topic of philosophical inquiry, especially in Aristotle, and subsequently since the 17th and 18th centuries, when the 'science of man' began to probe into human motivation and emotion. For writers such as the French moralists, or normatively suitable for the moralist Francis Hutcheson (1694-1746), David Hume (1711-76), Adam Smith (1723-90) and Immanuel Kant (1724-1804), a prime task was to delineate the variety of human reactions and motivations. Such an inquiry would locate our propensity for moral thinking among other faculties, such as perception and reason, and other tendencies, such as empathy, sympathy or self-interest. The task continues especially in the light of a post-Darwinian understanding of us. In like ways, the custom style of manners, extend the habitude to construct according to some conventional standard, wherefrom the formalities affected by such self-conscious realism, as applied to the judgements of ethics, and to the values, obligations, rights, etc., that are referred to in ethical theory. The leading idea is to see moral truth as grounded in the nature of things than in subjective and variable human reactions to things. Like realism in other areas, this is capable of many different formulations. Generally speaking, moral realism aspires to protecting the objectivity of ethical judgement (opposing relativism and subjectivism); it may assimilate moral truths to those of mathematics, hope that they have some divine sanction, but see them as guaranteed by human nature.
Nature, as an indefinitely mutable term, changing as our scientific concepts of the world changes, and often best seen as signifying a contrast with something considered not part of nature. The term applies both to individual species and also to the natural world as a whole. The association of what is natural with what it is good to become is visible in Plato, and is the central idea of Aristotle's philosophy of nature. Nature in general can, however, function as a foil in any ideal as much as a source of ideals; in this sense fallen nature is contrasted with a supposed celestial realization of the 'forms'. Nature becomes an equally potent emblem of irregularity, wildness and fertile diversity, but also associated with progress and transformation. Different conceptions of nature continue to have ethical overtones, for example, the conception of 'nature red in tooth and claw' often provides a justification for aggressive personal and political relations, or the idea that it is a woman's nature to be one thing or another is taken to be a justification for differential social expectations. Here the term functions as a fig-leaf for a particular set of stereotypes, and is a proper target of much feminist writing.
The central problem for naturalism is to define what counts as a satisfactory accommodation between the preferred science and the elements that on the face of it has no place in them. Alternatives include 'instrumentalism', 'reductionism' and 'eliminativism' as well as a variety of other anti-realist suggestions. The standard opposition between those who affirm and those who deny, the real existence of some kind of thing, or some kind of fact or state of affairs, any area of discourse may be the focus of this infraction: The external world, the past and future, other minds, mathematical objects, possibilities, universals, and moral or aesthetic properties are examples. The term naturalism is sometimes used for specific versions of these approaches in particular in ethics as the doctrine that moral predicates actually express the same thing as predicates from some natural or empirical science. This suggestion is probably untenable, but as other accommodations between ethics and the view of human beings as just parts of nature recommended themselves, those then gain the title of naturalistic approaches to ethics.
By comparison with nature which may include (1) that which is deformed or grotesque, or fails to achieve its proper form or function, or just the statistically uncommon or unfamiliar, (2) the supernatural, or the world of gods and invisible agencies, (3) the world of rationality and intelligence, of a kind to be readily understood as capable of being distinguished as differing from the biological and physical order, (4) that which is manufactured and artifactual, or the product of human invention, and (5) related to it, the world of convention and artifice.
Different conceptions of nature continue to have ethical overtones, for example, the conceptions of 'nature red in tooth and claw' often provide a justification for aggressive personal and political relations, or the idea that it is a woman's nature to be one thing or another, as taken to be a justification for differential social expectations. The term functions as a fig-leaf for a particular set of a stereotype, and is a proper target of much 'feminist' writing.
This brings to question, that most of all ethics are contributively distributed as an understanding for which a dynamic function in and among the problems that are affiliated with human desire and needs the achievements of happiness, or the distribution of goods. The central problem specific to thinking about the environment is the independent value to place on 'such-things' as preservation of species, or protection of the wilderness. Such protection can be supported as a man to ordinary human ends, for instance, when animals are regarded as future sources of medicines or other benefits. Nonetheless, many would want to claim a non-utilitarian, absolute value for the existence of wild things and wild places. It is in their value that things consist. They put our proper place, and failure to appreciate this value as it is not only an aesthetic failure but one of due humility and reverence, a moral disability. The problem is one of expressing this value, and mobilizing it against utilitarian agents for developing natural areas and exterminating species, more or less at will.
Many concerns and disputed clusters around the idea associated with the term 'substance'. The substance of a thing may be considered in: (1) its essence, or that which makes it what it is. This will ensure that the substance of a thing is that which remains through change in properties. Again, in Aristotle, this essence becomes more than just the matter, but a unity of matter and form. (2) That which can exist by itself, or does not need a subject for existence, in the way that properties need objects, hence (3) that which bears properties, as a substance is then the subject of predication, that about which things are said as opposed to the things said about it. Substance in the last two senses stands opposed to modifications such as quantity, quality, relations, etc. it is hard to keep this set of ideas distinct from the doubtful notion of a substratum, something distinct from any of its properties, and hence, as an incapable characterization. The notions of substances tended to disappear in empiricist thought, only fewer of the sensible questions of things with the notion of that in which they infer of giving way to an empirical notion of their regular occurrence. However, this is in turn is problematic, since it only makes sense to talk of the occurrence of only instances of qualities, not of quantities themselves, yet the problem of what it is for a quality value to be the instance that remains.
Metaphysics inspired by modern science tend to reject the concept of substance in favour of concepts such as that of a field or a process, each of which may seem to provide a better example of a fundamental physical category.
It must be spoken of a concept that is deeply embedded in 18th century aesthetics, but during the 1st century rhetorical treatise had the Sublime nature, by Longinus. The sublime is great, fearful, noble, calculated to arouse sentiments of pride and majesty, as well as awe and sometimes terror. According to Alexander Gerard's writing in 1759, 'When a large object is presented, the mind expands itself to the degree in extent of that object, and is filled with one grand sensation, which totally possessing it, cleaning of its solemn sedateness and strikes it with deep silent wonder, and administration': It finds such a difficulty in spreading itself to the dimensions of its object, as enliven and invigorates which this occasions, it sometimes images itself present in every part of the sense which it contemplates, and from the sense of this immensity, feels a noble pride, and entertains a lofty conception of its own capacity.
In Kant's aesthetic theory the sublime 'raises the soul above the height of vulgar complacency'. We experience the vast spectacles of nature as 'absolutely great' and of irresistible force and power. This perception is fearful, but by conquering this fear, and by regarding as small 'those things of which we are wont to be solicitous' we quicken our sense of moral freedom. So we turn the experience of frailty and impotence into one of our true, inward moral freedom as the mind triumphs over nature, and it is this triumph of reason that is truly sublime. Kant thus paradoxically places our sense of the sublime in an awareness of us as transcending nature, than in an awareness of us as a frail and insignificant part of it.
Nevertheless, the doctrine that all relations are internal was a cardinal thesis of absolute idealism, and a central point of attack by the British philosopher's George Edward Moore (1873-1958) and Bertrand Russell (1872-1970). It is a kind of 'essentialism', stating that if two things stand in some relationship, then they could not be what they are, did they not do so, if, for instance, I am wearing a hat mow, then when we imagine a possible situation that we would be got to describe as my not wearing the hat now, we would strictly not be imaging as one and the hat, but only some different individual.
The countering partitions a doctrine that bears some resemblance to the metaphysically based view of the German philosopher and mathematician Gottfried Leibniz (1646-1716) that if a person had any other attributes that the ones he has, he would not have been the same person. Leibniz thought that when asked what would have happened if Peter had not denied Christ. That being that if I am asking what had happened if Peter had not been Peter, denying Christ is contained in the complete notion of Peter. But he allowed that by the name 'Peter' might be understood as 'what is involved in those attributes [of Peter] from which the denial does not follow'. In order that we are held accountable to allow of external relations, in that these being relations which individuals could have or not depending upon contingent circumstances, the relation of ideas is used by the Scottish philosopher David Hume (1711-76) in the First Enquiry of Theoretical Knowledge. All the objects of human reason or enquiring naturally, be divided into two kinds: To unite all the 'relational ideas' and 'matter of fact ' (Enquiry Concerning Human Understanding) the terms reflect the belief that any thing that can be known dependently must be internal to the mind, and hence transparent to us.
In Hume, objects of knowledge are divided into matter of fact (roughly empirical things known by means of impressions) and the relation of ideas. The contrast, also called 'Hume's Fork', is a version of the speculative deductive reasoning is an outcry for characteristic distinction, but ponderously reflects about the 17th and early 18th centuries, behind that the deductivist is founded by chains of infinite certainty as comparative ideas. It is extremely important that in the period between Descartes and J.S. Mill that a demonstration is not, but only a chain of 'intuitive' comparable ideas, whereby a principle or maxim can be established by reason alone. It is in this sense that the English philosopher John Locke (1632-1704) who believed that theologically and moral principles are capable of demonstration, and Hume denies that they are, and also denies that scientific enquiries proceed in demonstrating its results.
A mathematical proof is formally inferred as to an argument that is used to show the truth of a mathematical assertion. In modern mathematics, a proof begins with one or more statements called premises and demonstrate, using the rules of logic, that if the premises are true then a particular conclusion must also be true.
The accepted methods and strategies used to construct a convincing mathematical argument have evolved since ancient times and continue to change. Consider the Pythagorean Theorem, named after the 5th century Bc. Greek mathematician and philosopher Pythagoras, stated that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. Many early civilizations considered this theorem true because it agreed with their observations in practical situations. But the early Greeks, among others, realized that observation and commonly held opinions do not guarantee mathematical truth. For example, before the 5th century Bc it was widely believed that all lengths could be expressed as the ratio of two whole numbers, but an unknown Greek mathematician proved that this was not true by showing that the length of the diagonal of a square with an area of one is the irrational number Ã.
The Greek mathematician Euclid laid down some of the conventions central to modern mathematical proofs. His book The Elements, written about 300 Bc, contains many proofs in the fields of geometry and algebra. This book illustrates the Greek practice of writing mathematical proofs by first clearly identifying the initial assumptions and then reasoning from them in a logical way in order to obtain a desired conclusion. As part of such an argument, Euclid used results that had already been shown to be true, called theorems, or statements that were explicitly acknowledged to be self-evident, called axioms; this practice continues today.
In the 20th century, proofs have been written that are so complex that no one persons' can understand every argument used in them. In 1976, a computer was used to complete the proof of the four-colour theorem. This theorem states that four colours are sufficient to colour any map in such a way that regions with a common boundary line have different colours. The use of a computer in this proof inspired considerable debate in the mathematical community. At issue was whether a theorem can be considered proven if human beings have not actually checked every detail of the proof?
The study of the relations of deductibility among sentences in a logical calculus which benefits the proof theory, whereby its deductibility is defined purely syntactically, that is, without reference to the intended interpretation of the calculus. The subject was founded by the mathematician David Hilbert (1862-1943) in the hope that strictly finitely methods would provide a way of proving the consistency of classical mathematics, but the ambition was torpedoed by Gödel's second incompleteness theorem.
The deductibility between formulae of a system, but once the notion of an interpretation is in place we can ask whether a formal system meets certain conditions. In particular, can it lead us from sentences that are true under some interpretation? And if a sentence is true under all interpretations, is it also a theorem of the system? We can define a notion of validity (a formula is valid if it is true in all interpreted rations) and semantic consequence (a formula 'B' is a semantic consequence of a set of formulae, written {A1 . . . An} ⊨ B, if it is true in all interpretations in which they are true) Then the central questions for a calculus will be whether all and only its theorems are valid, and whether {A1 . . . An}? B if and only if {A1 . . . An}? B. There are the questions of the soundness and completeness of a formal system. For the propositional calculus this turns into the question of whether the proof theory delivers as theorems all and only 'tautologies'. There are many axiomatizations of the propositional calculus that are consistent and complete. The mathematical logician Kurt Gödel (1906-78) proved in 1929 that the first-order predicate under every interpretation is a theorem of the calculus.
The Euclidean geometry is the greatest example of the pure 'axiomatic method', and as such had incalculable philosophical influence as a paradigm of rational certainty. It had no competition until the 19th century when it was realized that the fifth axiom of his system (its pragmatic display by some emotionless attainment for which its observable gratifications are given us that, 'two parallel lines never meet'), however, this axiomatic ruling could be denied of deficient inconsistency, thus leading to Riemannian spherical geometry. The significance of Riemannian geometry lies in its use and extension of both Euclidean geometry and the geometry of surfaces, leading to a number of generalized differential geometries. It's most important effect was that it made a geometrical application possible for some major abstractions of tensor analysis, leading to the pattern and concepts for general relativity later used by Albert Einstein in developing his theory of relativity. Riemannian geometry is also necessary for treating electricity and magnetism in the framework of general relativity. The fifth chapter of Euclid's Elements, is attributed to the mathematician Eudoxus, and contains a precise development of the real number, work which remained unappreciated until rediscovered in the 19th century.
The Axiom, in logic and mathematics, is a basic principle that is assumed to be true without proof. The use of axioms in mathematics stems from the ancient Greeks, most probably during the 5th century Bc, and represents the beginnings of pure mathematics as it is known today. Examples of axioms are the following: 'No sentence can be true and false at the same time' (the principle of contradiction); 'If equals are added to equals, the sums are equal'. 'The whole is greater than any of its parts'. Logic and pure mathematics begin with such unproved assumptions from which other propositions (theorems) are derived. This procedure is necessary to avoid circularity, or an infinite regression in reasoning. The axioms of any system must be consistent with one-another, that is, they should not lead to contradictions. They should be independent in the sense that they cannot be derived from one-another. They should also be few in number. Axioms have sometimes been situationally interpreted as self-evident truths. The present tendency is to avoid this claim and simply to assert that an axiom is assumed to be true without proof in the system of which it is a part.
The terms 'axiom' and 'postulate' are often used synonymously. Sometimes the word axiom is used to refer to basic principles that are assumed by every deductive system, and the term postulate is used to refer to first principles peculiar to a particular system, such as Euclidean geometry. Infrequently, the word axiom is used to refer to first principles in logic, and the term postulate is used to refer to first principles in mathematics.
The applications of game theory are wide-ranging and account for steadily growing interest in the subject. Von Neumann and Morgenstern indicated the immediate utility of their work on mathematical game theory by linking it with economic behaviour. Models can be developed, in fact, for markets of various commodities with differing numbers of buyers and sellers, fluctuating values of supply and demand, and seasonal and cyclical variations, as well as significant structural differences in the economies concerned. Here game theory is especially relevant to the analysis of conflicts of interest in maximizing profits and promoting the widest distribution of goods and services. Equitable division of property and of inheritance is another area of legal and economic concern that can be studied with the techniques of game theory.
In the social sciences, n-person game theory has interesting uses in studying, for example, the distribution of power in legislative procedures. This problem can be interpreted as a three-person game at the congressional level involving vetoes of the president and votes of representatives and senators, analysed in terms of successful or failed coalitions to pass a given bill. Problems of majority rule and individual decision makes are also amenable to such study.
Sociologists have developed an entire branch of game theory devoted to the study of issues involving group decision making. Epidemiologists also make use of game theory, especially with respect to immunization procedures and methods of testing a vaccine or other medication. Military strategists turn to game theory to study conflicts of interest resolved through 'battles' where the outcome or payoff of a given war game is either victory or defeat. Usually, such games are not examples of zero-sum games, for what one player loses in terms of lives and injuries are not won by the victor. Some uses of game theory in analyses of political and military events have been criticized as a dehumanizing and potentially dangerous oversimplification of necessarily complicating factors. Analysis of economic situations is also usually more complicated than zero-sum games because of the production of goods and services within the play of a given 'game'.
All is the same in the classical theory of the syllogism; a term in a categorical proposition is distributed if the proposition entails any proposition obtained from it by substituting a term denoted by the original. For example, in 'all dogs bark' the term 'dogs' is distributed, since it entails 'all terriers' bark', which is obtained from it by a substitution. In 'Not all dogs bark', the same term is not distributed, since it may be true while 'not all terriers' bark' is false.
When a representation of one system by another is usually more familiar, in and for itself that those extended in representation that their workings are supposed analogously to that of the first. This one might model the behaviour of a sound wave upon that of waves in water, or the behaviour of a gas upon that to a volume containing moving billiard balls. While nobody doubts that models have a useful 'heuristic' role in science, there has been intense debate over whether a good model, or whether an organized structure of laws from which it can be deduced and suffices for scientific explanation. As such, the debate of content was inaugurated by the French physicist Pierre Marie Maurice Duhem (1861-1916), in 'The Aim and Structure of Physical Theory' (1954) by which Duhem's conception of science is that it is simply a device for calculating as science provides deductive system that is systematic, economical, and predictive, but not that represents the deep underlying nature of reality. Steadfast and holding of its contributive thesis that in isolation, and since other auxiliary hypotheses will always be needed to draw empirical consequences from it. The Duhem thesis implies that refutation is a more complex matter than might appear. It is sometimes framed as the view that a single hypothesis may be retained in the face of any adverse empirical evidence, if we prepared to make modifications elsewhere in our system, although strictly speaking this is a stronger thesis, since it may be psychologically impossible to make consistent revisions in a belief system to accommodate, say, the hypothesis that there is a hippopotamus in the room when visibly there is not.
Primary and secondary qualities are the division associated with the 17th-century rise of modern science, wit h its recognition that the fundamental explanatory properties of things that are not the qualities that perception most immediately concerns. They're later are the secondary qualities, or immediate sensory qualities, including colour, taste, smell, felt warmth or texture, and sound. The primary properties are less tied to their deliverance of one particular sense, and include the size, shape, and motion of objects. In Robert Boyle (1627-92) and John Locke (1632-1704) the primary qualities are applicably befitting the properly occupying importance in the integration of incorporating the scientifically tractable unification, objective qualities essential to anything material, are of a minimal listing of size, shape, and mobility, i.e., the states of being at rest or moving. Locke sometimes adds number, solidity, texture (where this is thought of as the structure of a substance, or way in which it is made out of atoms). The secondary qualities are the powers to excite particular sensory modifications in observers. Once, again, that Locke himself thought in terms of identifying these powers with the texture of objects that, according to corpuscularian science of the time, were the basis of an object's causal capacities. The ideas of secondary qualities are sharply different from these powers, and afford us no accurate impression of them. For Renè Descartes (1596-1650), this is the basis for rejecting any attempt to think of knowledge of external objects as provided by the senses. But in Locke our ideas of primary qualities do afford us an accurate notion of what shape, size. And mobility is. In English-speaking philosophy the first major discontent with the division was voiced by the Irish idealist George Berkeley (1685-1753), who probably took for a basis of his attack from Pierre Bayle (1647-1706), who in turn cites the French critic Simon Foucher (1644-96). Modern thought continues to wrestle with the difficulties of thinking of colour, taste, smell, warmth, and sound as real or objective properties to things independent of us.
The proposal set forth that characterizes the 'modality' of a proposition as the notion for which it is true or false. The most important division is between propositions true of necessity, and those true as things are: Necessary as opposed to contingent propositions. Other qualifiers sometimes called 'modal' include the tense indicators, 'it will be the case that 'p', or 'it was not of the situations that 'p', and there are affinities between the 'deontic' indicators, 'it should be the case that 'p', or 'it is permissible that 'p', and the necessity and possibility.
The aim of logic is to make explicitly the rules by which inferences may be drawn, than to study the actual reasoning processes that people use, which may or may not conform to those rules. In the case of deductive logic, if we ask why we need to obey the rules, the most general form of the answer is that if we do not we contradict ourselves, or strictly speaking, we stand ready to contradict ourselves. Someone failing to draw a conclusion that follows from a set of premises need not be contradicting him or herself, but only failing to notice something. However, he or she is not defended against adding the contradictory conclusion to his or her set of beliefs. There is no equally simple answer in the case of inductive logic, which is in general a less robust subject, but the aim will be to find reasoning such that anyone failing to conform to it will have improbable beliefs. Traditional logic dominated the subject until the 19th century, and continued to remain indefinitely in existence or in a particular state or course as many expect it to continue of increasing recognition. Occurring to matters right or obtainable, the complex of ideals, beliefs, or standards that characterize or pervade a totality of infinite time. Existing or dealing with what exists only the mind is congruently responsible for presenting such to an image or lifelike imitation of representing contemporary philosophy of mind, following cognitive science, if it uses the term 'representation' to mean just about anything that can be semantically evaluated. Thus, representations may be said to be true, as to connect with the arousing truth-of something to be about something, and to be exacting, etc. Envisioned ideations come in many varieties. The most familiar are pictures, three-dimensional models (e.g., statues, scale models), linguistic text, including mathematical formulas and various hybrids of these such as diagrams, maps, graphs and tables. It is an open question in cognitive science whether mental representation falls within any of these familiar sorts.
The representational theory of cognition is uncontroversial in contemporary cognitive science that cognitive processes are processes that manipulate representations. This idea seems nearly inevitable. What makes the difference between processes that are cognitive - solving a problem - and those that are not - a patellar reflex, for example - are just that cognitive processes are epistemically assessable? A solution procedure can be justified or correct; a reflex cannot. Since only things with content can be epistemically assessed, processes appear to count as cognitive only in so far as they implicate representations.
It is tempting to think that thoughts are the mind's representations: Aren't thoughts just those mental states that have semantic content? This is, no doubt, harmless enough provided we keep in mind that the scientific study of processes of awareness, thoughts, and mental organizations, often by means of computer modelling or artificial intelligence research that the cognitive aspect of meaning of a sentence may attribute this thought of as its content, or what is strictly said, abstracted away from the tone or emotive meaning, or other implicatures generated, for example, by the choice of words. The cognitive aspect is what has to be understood to know what would make the sentence true or false: It is frequently identified with the 'truth condition' of the sentence. The truth condition of a statement is the condition the world must meet if the statement is to be true. To know this condition is equivalent to knowing the meaning of the statement. Although this sounds as if it gives a solid anchorage for meaning, some of the security disappears when it turns out that the truth condition can only be defined by repeating the very same statement: The truth condition of 'snow is white' is that snow is white: The truth condition of 'Britain would have capitulated had Hitler invaded' is that Britain would have capitulated had Hitler invaded. It is disputed whether this element of running-on-the-spot disqualifies truth conditions from playing the central role in a substantive theory of meaning. Truth-conditional theories of meaning are sometimes opposed by the view that to know the meaning of a statement is to be able to use it in a network of inferences.
The view that the role of sentences in inference gives a more important key to their meaning than their 'external' relations to things in the world is that the meaning of a sentence becomes its place in a network of inferences that it legitimates. Also, known as functional role semantics, procedural semantics, or conceptual role semantics. The view bears some relation to the coherence theory of truth, and suffers from the same suspicion that it divorces meaning from any clear association with things in the world.
Moreover, internalist theories take the content of a representation to be a matter determined by factors internal to the system that uses it. Thus, what Block (1986) calls 'short-armed' functioning role theories are internalist. Externalist theories take on or upon the content of representation to be determined, in part, at least, by factors external to the system that uses it. Covariance theories, as well as teleological theories that invoke a historical theory of functions, take content to be determined by 'external' factors, crossing the atomist-holistic distinction with the internalist-externalist distinction.
Externalist theories, sometimes called non-individualistic theories, have the consequence that molecule for molecule identical cognitive systems might yet harbour representations with different contents. This has given rise to a controversy concerning 'narrow' content. If we assume some form of externalist theory is correct, then content is, in the first instance 'wide' content, i.e., determined in part by factors external to the representing system. On the other hand, it seems clear that, on plausible assumptions about how to individuate psychological capacities, internally equivalent systems must have the same psychological capacities. Hence, it would appear that wide content cannot be relevant to characterizing psychological equivalence. Since cognitive science generally assumes that content is relevant to characterizing psychological equivalence, philosophers attracted to externalist theories of content have sometimes attempted to introduce 'narrow' content, i.e., an aspect or kind of content that is equivalent in internally equivalent systems. The simplest such theory is Fodor's idea (1987) that narrow content is a function from context, i.e., from whatever the external factors are to wide contents.
Most briefly, the epistemological tradition has been internalist, with externalism emerging as a genuine option only in the twentieth century. Te best way to clarify this distinction is by considering another way: That between knowledge and justification. Knowledge has been traditionally defined as justified true belief. However, due to certain counter-examples, the definition had to be redefined. With possible situations in which objectifies abuse are made the chief ambition for the aim assigned to target beliefs, and, perhaps, might be both true and justified, but still intuitively certain we would not call it knowledge. The extra element of undefeatedness attempts to rule out the counter-examples. In that, the relevant issue, at this point, is that on all accounts of it, knowledge entails truth: One can't know something false, as justification, on the other hand, is the account of the reason one hands for a belief. However, one may be justified in holding a false belief, justification is understood from the subject's point of view, and it doesn't entail truth.
Internalism is the position that says that the reason one has for a belief, its justification, must be in some sense available to the knowing subject. If one has a belief, and the reason why it is acceptable for me to hold that belief is not knowable to the person in question, then there is no justification. Externalism holds that it is possible for a person to have a justified belief without having access to the reason for it. Perhaps, that this view seems too stringent to the externalist, who can explain such cases by, for example, appeal to the use of a process that reliable produced truths. One can use perception to acquire beliefs, and the very use of such a reliable method ensures that the belief is a true belief. Nonetheless, some externalists have produced accounts of knowledge with relativistic aspects to them. Alvin Goldman, who posses as an intellectual, has undertaken the hold on the verifiable body of things known about or in science. This, orderers contributing the insight known for a relativistic account of knowledge in, his writing of, Epistemology and Cognition (1986). Such accounts use the notion of a system of rules for the justification of belief - these rules provide a framework within which it can be established whether a belief is justified or not. The rules are not to be understood as actually conscious guiding the dogmatizer's thought processes, but rather can be applied from without to give an objective judgement as to whether the beliefs are justified or not. The framework establishes what counts as justification, and like criterions established the framework. Genuinely epistemic terms like 'justification' occur in the context of the framework, while the criterion, attempts to set up the framework without using epistemic terms, using purely factual or descriptive terms.
In any event, a standard psycholinguistic theory, for instance, hypothesizes the construction of representations of the syntactic structures of the utterances one hears and understands. Yet we are not aware of, and non-specialists do not even understand, the structures represented. Thus, cognitive science may attribute thoughts where common sense would not. Second, cognitive science may find it useful to individuate thoughts in ways foreign to common sense.
The representational theory of cognition gives rise to a natural theory of intentional stares, such as believing, desiring and intending. According to this theory, intentional state factors are placed into two aspects: A 'functional' aspect that distinguishes believing from desiring and so on, and a 'content' aspect that distinguishes belief from each other, desires from each other, and so on. A belief that 'p' might be realized as a representation with the content that 'p' and the function of serving as a premise in inference, as a desire that 'p' might be realized as a representation with the content that 'p' and the function of intimating processing designed to bring about that 'p' and terminating such processing when a belief that 'p' is formed.
A great deal of philosophical effort has been lavished on the attempt to naturalize content, i.e., to explain in non-semantic, non-intentional terms what it is for something to be a representation (have content), and what it is for something to have some particular content than some other. There appear to be only four types of theory that have been proposed: Theories that ground representation in (1) similarity, (2) covariance, (3) functional roles, (4) teleology.
Similar theories had that 'r' represents 'x' in virtue of being similar to 'x'. This has seemed hopeless to most as a theory of mental representation because it appears to require that things in the brain must share properties with the things they represent: To represent a cat as furry appears to require something furry in the brain. Perhaps a notion of similarity that is naturalistic and does not involve property sharing can be worked out, but it is not obviously how.
Covariance theories hold that r's represent 'x' is grounded in the fact that r's occurrence ovaries with that of 'x'. This is most compelling when one thinks about detection systems: The firing neuron structure in the visual system is said to represent vertical orientations if it's firing ovaries with the occurrence of vertical lines in the visual field. Dretske (1981) and Fodor (1987), has in different ways, attempted to promote this idea into a general theory of content.
'Content' has become a technical term in philosophy for whatever it is a representation has that makes it semantically evaluable. Thus, a statement is sometimes said to have a proposition or truth condition s its content: a term is sometimes said to have a concept as its content. Much less is known about how to characterize the contents of non-linguistic representations than is known about characterizing linguistic representations. 'Content' is a useful term precisely because it allows one to abstract away from questions about what semantic properties representations have: a representation's content is just whatever it is that underwrites its semantic evaluation.
Likewise, functional role theories hold that r's representing 'x' is grounded in the functional role 'r' has in the representing system, i.e., on the relations imposed by specified cognitive processes between 'r' and other representations in the system's repertoire. Functional role theories take their cue from such common sense ideas as that people cannot believe that cats are furry if they do not know that cats are animals or that fur is like hair.
What is more that theories of representational content may be classified according to whether they are atomistic or holistic and according to whether they are externalistic or internalistic? The most generally accepted account of this distinction is that a theory of justification is internalist if and only if it requires that all of the factors needed for a belief to be epistemically justified for a given person be cognitively accessible to that person, internal to his cognitive perspective, and externalist, if it allows hast at least some of the justifying factors need not be thus accessible, so that they can be external to the believer's cognitive perspective, beyond his ken. However, epistemologists often use the distinction between internalist and externalist theories of epistemic justification without offering and very explicit explications.
Atomistic theories take a representation's content to be something that can be specified independently of that representation's relations to other representations. What Fodor (1987) calls the crude causal theory, for example, takes a representation to be a
cow
- a mental representation with the same content as the word 'cow' - if its tokens are caused by instantiations of the property of being-a-cow, and this is a condition that places no explicit constraint on how
cow
’s must or might relate to other representations.
The syllogistic or categorical syllogism is the inference of one proposition from two premises. For example is, 'all horses have tails, and things with tails are four legged, so all horses are four legged. Each premise has one term in common with the other premises. The terms that do not occur in the conclusion are called the middle term. The major premise of the syllogism is the premise containing the predicate of the contraction (the major term). And the minor premise contains its subject (the minor term), justly as commended of the first premise of the example, in the minor premise the second the major term, so the first premise of the example is the minor premise, the second the major premise and 'having a tail' is the middle term. This enables syllogisms that there of a classification, that according to the form of the premises and the conclusions. The other classification is by figure, or way in which the middle term is placed or way in within the middle term is placed in the premise.
Although the theory of the syllogism dominated logic until the 19th century, it remained a piecemeal affair, able to deal with only relations valid forms of valid forms of argument. There have subsequently been rearguing actions attempting, but in general it has been eclipsed by the modern theory of quantification, the predicate calculus is the heart of modern logic, having proved capable of formalizing the calculus rationing processes of modern mathematics and science. In a first-order predicate calculus the variables range over objects: In a higher-order calculus the might range over predicate and functions themselves. The fist-order predicated calculus with identity includes '=' as primitive (undefined) expression: In a higher-order calculus. It may be defined by law that? = y if (? F) (F? - Fy), which gives greater expressive power for less complexity.
Modal logic was of great importance historically, particularly in the light of the deity, but was not a central topic of modern logic in its gold period as the beginning of the 20th century. It was, however, revived by the American logician and philosopher Irving Lewis (1883-1964), although he wrote extensively on most central philosophical topics, he is remembered principally as a critic of the intentional nature of modern logic, and as the founding father of modal logic. His independent proofs worth showing that from a contradiction anything follows its parallelled logic, using a notion of entailment stronger than that of strict implication.
The imparting information has been conduced or carried out of the prescribed conventions, as disconcerting formalities that blend upon the plexuities of circumstance, that takes place in the folly of depending the contingence too secure of possibilities the outlook to be entering one's mind. This may arouse of what is proper or acceptable in the interests of applicability, which from time to time of increasingly forward as placed upon the occasion that various doctrines concerning the necessary properties are themselves represented by an arbiter or a conventional device used for adding to a prepositional or predicated calculus, for its additional rationality that two operators? And? (Sometimes written 'N' and 'M'), meaning necessarily and possible, respectfully. Usually, the production necessitates the likelihood of ‘p’, and 'p’ and ‘p’. While equalled in of wanting, as these controversial subscriptions include ‘p’ and ‘p’, if a proposition is necessary. It's necessarily, characteristic of a system known as S4, and ‘P’, ‘p’ (if as preposition is possible, it's necessarily possible, characteristic of the system known as S5). In classical modal realism, the doctrine advocated by David Lewis (1941-2002), that different possible worlds care to be thought of as existing exactly as this one does. Thinking in terms of possibilities is thinking of real worlds where things are different. The view has been charged with making it impossible to see why it is good to save the child from drowning, since there is still a possible world in which she for her counterpart. Saying drowned, is spoken from the standpoint of the universe that it should make no difference which world is actual. Critics also charge that the notion fails to fit either with a coherent Theory of how we know about possible worlds, or with a coherent theory of why we are interested in them, but Lewis denied that any other way of interpreting modal statements is tenable.
Saul Kripke (1940- ), the American logician and philosopher contributed to the classical modern treatment of the topic of reference, by its clarifying distinction between names and definite description, and opening the door to many subsequent attempts to understand the notion of reference in terms of a causal link between the use of a term and an original episode of attaching a name to the subject.
One of the three branches into which 'semiotic' is usually divided, the study of semantically meaning of words, and the relation of signs to the degree to which the designs are applicable, in that, in formal studies, semantics is provided for by a formal language when an interpretation of 'model' is specified. However, a natural language comes ready interpreted, and the semantic problem is not that of the specification but of understanding the relationship between terms of various categories (names, descriptions, predicate, adverbs . . . ) and their meaning. An influential proposal by attempting to provide a truth definition for the language, which will involve giving a full structure of different kinds, has on the truth conditions of sentences containing them.
Holding that the basic case of reference is the relation between a name and the persons or objective worth which it names, its philosophical problems include trying to elucidate that relation, to understand whether other semantic relations, such s that between a predicate and the property it expresses, or that between a description of what it describes, or that between me and the word 'I', are examples of the same relation or of very different ones. A great deal of modern work on this was stimulated by the American logician Saul Kripke's, Naming and Necessity (1970). It would also be desirable to know whether we can refer to such things as objects and how to conduct the debate about each and issue. A popular approach, following Gottlob Frége, is to argue that the fundamental unit of analysis should be the whole sentence. The reference of a term becomes a derivative notion it is whatever it is that defines the term's contribution to the trued condition of the whole sentence. There need be nothing further to say about it, given that we have a way of understanding the attribution of meaning or truth-condition to sentences. Other approaches in searching for more substantive possibilities that causality or psychological or social constituents are pronounced between words and things.
However, following Ramsey and the Italian mathematician G. Peano (1858-1932), it has been customary to distinguish logical paradoxes that depend upon a notion of reference or truth (semantic notions) such as those of the 'Liar family', which form the purely logical paradoxes in which no such notions are involved, such as Russell's paradox, or those of Canto and Burali-Forti. Paradoxes of the fist type seem to depend upon an element of a self-reference, in which a sentence is about itself, or in which a phrase refers to something about itself, or in which a phrase refers to something defined by a set of phrases of which it is itself one. It is to feel that this element is responsible for the contradictions, although mind-reference itself is often benign (for instance, the sentence 'All English sentences should have a verb', includes itself happily in the domain of sentences it is talking about), so the difficulty lies in forming a condition that is only existentially pathological and resulting of a self-reference. Paradoxes of the second kind then need a different treatment. Whilst the distinction is convenient in allowing set theory to proceed by circumventing the latter paradoxes by technical mans, even when there is no solution to the semantic paradoxes, it may be a way of ignoring the similarities between the two families. There is still the possibility that while there is no agreed solution to the semantic paradoxes. Our understanding of Russell's paradox may be imperfect as well.
Truth and falsity are two classical truth-values that a statement, proposition or sentence can take, as it is supposed in classical (two-valued) logic, that each statement has one of these values, and 'none' has both. A statement is then false if and only if it is not true. The basis of this scheme is that to each statement there corresponds a determinate truth condition, or way the world must be for it to be true: If this condition obtains, the statement is true, and otherwise false. Statements may indeed be felicitous or infelicitous in other dimensions (polite, misleading, apposite, witty, etc.) but truth is the central normative notion governing assertion. Considerations of vagueness may introduce greys into this black-and-white scheme. For the issue to be true, any suppressed premise or background framework of thought necessary makes an agreement valid, or a tenable position, as a proposition whose truth is necessary for either the truth or the falsity of another statement. Thus if 'p' presupposes 'q', 'q' must be true for 'p' to be either true or false. In the theory of knowledge, the English philosopher and historian George Collingwood (1889-1943), announces that any proposition capable of truth or falsity stands on of 'absolute presuppositions' which are not properly capable of truth or falsity, since a system of thought will contain no way of approaching such a question (a similar idea later voiced by Wittgenstein in his work On Certainty). The introduction of presupposition therefore means that either another of a truth value is found, 'intermediate' between truth and falsity, or the classical logic is preserved, but it is impossible to tell whether a particular sentence empresses a preposition that is a candidate for truth and falsity, without knowing more than the formation rules of the language. Each suggestion directionally imparts as to convey there to some consensus that at least who where definite descriptions are involved, examples equally given by regarding the overall sentence as false as the existence claim fails, and explaining the data that the English philosopher Frederick Strawson (1919-) relied upon as the effects of 'implicatures'.
Views about the meaning of terms will often depend on classifying the implicatures of sayings involving the terms as implicatures or as genuine logical implications of what is said. Implicatures may be divided into two kinds: Conversational implicatures of the two kinds and the more subtle category of conventional implicatures. A term may as a matter of convention carries and pushes in controversial implicatures. Thus, one of the relations between 'he is poor and honest' and 'he is poor but honest' is that they have the same content (are true in just the same conditional) but the second has implicatures (that the combination is surprising or significant) that the first lacks.
It is, nonetheless, that we find in classical logic a proposition that may be true or false. In that, if the former, it is said to take the truth-value true, and if the latter the truth-value false. The idea behind the terminological phrases is the analogue between assigning a propositional variable one or other of these values, as is done in providing an interpretation for a formula of the propositional calculus, and assigning an object as the value of any other variable. Logics with intermediate value are called 'many-valued logics'.
Nevertheless, an existing definition of the predicate' . . . is true' for a language that satisfies convention 'T', the material adequately condition laid down by Alfred Tarski, born Alfred Teitelbaum (1901-83), whereby his methods of 'recursive' definition, enabling us to say for each sentence what it is that its truth consists in, but giving no verbal definition of truth itself. The recursive definition or the truth predicate of a language is always provided in a 'metalanguage', Tarski is thus committed to a hierarchy of languages, each with it’s associated, but different truth-predicate. While this enables an easier approach to avoid the contradictions of paradoxical contemplations, it yet conflicts with the idea that a language should be able to say everything that there is to say, and other approaches have become increasingly important.
So, that the truth condition of a statement is the condition for which the world must meet if the statement is to be true. To know this condition is equivalent to knowing the meaning of the statement. Although this sounds as if it gives a solid anchorage for meaning, some of the securities disappear when it turns out that the truth condition can only be defined by repeating the very same statement: The truth condition of 'now is white' is that 'snow is white', the truth condition of 'Britain would have capitulated had Hitler invaded', is that 'Britain would have capitulated had Hitler invaded'. It is disputed whether this element of running-on-the-spot disqualifies truth conditions from playing the central role in a substantive theory of meaning. Truth-conditional theories of meaning are sometimes opposed by the view that to know the meaning of a statement is to be able to use it in a network of inferences.
Taken to be the view, inferential semantics takes upon the role of a sentence in inference, and gives a more important key to their meaning than this 'external' relation to things in the world. The meaning of a sentence becomes its place in a network of inferences that it legitimates. Also known as functional role semantics, procedural semantics, or conception to the coherence theory of truth, and suffers from the same suspicion that it divorces meaning from any clear association with things in the world.
Moreover, a theory of semantic truth is that of the view if language is provided with a truth definition, there is a sufficient characterization of its concept of truth, as there is no further philosophical chapter to write about truth: There is no further philosophical chapter to write about truth itself or truth as shared across different languages. The view is similar to the disquotational theory.
The redundancy theory, or also known as the 'deflationary view of truth' fathered by Gottlob Frége and the Cambridge mathematician and philosopher Frank Ramsey (1903-30), who showed how the distinction between the semantic paradoxes, such as that of the Liar, and Russell's paradox, made unnecessary the ramified type theory of Principia Mathematica, and the resulting axiom of reducibility. By taking all the sentences affirmed in a scientific theory that use some terms, e.g., quarks, and to a considerable degree of replacing the term by a variable instead of saying that quarks have such-and-such properties, the Ramsey sentence says that there is something that has those properties. If the process is repeated for all of a group of the theoretical terms, the sentence gives 'topic-neutral' structure of the theory, but removes any implication that we know what the terms so administered to advocate. It leaves open the possibility of identifying the theoretical item with whatever, but it is that best fits the description provided. However, it was pointed out by the Cambridge mathematician Newman, that if the process is carried out for all except the logical bones of a theory, then by the Löwenheim-Skolem theorem, the result will be interpretable, and the content of the theory may reasonably be felt to have been lost.
For in part, while, both Frége and Ramsey are agreeing that the essential claim is that the predicate' . . . is true' does not have a sense, i.e., expresses no substantive or profound or explanatory concept that ought to be the topic of philosophical enquiry. The approach admits of different versions, but centres on the points (1) that 'it is true that 'p' says no more nor less than 'p' (hence, redundancy): (2) that in less direct context, such as 'everything he said was true', or 'all logical consequences of true propositions are true', the predicate functions as a device enabling us to generalize than as an adjective or predicate describing the things he said, or the kinds of propositions that follow from a true preposition. For example, the second may translate as '(?p, q)(p & p? Q? q)' where there is no use of a notion of truth.
There are technical problems in interpreting all uses of the notion of truth in such ways; nevertheless, they are not generally felt to be insurmountable. The approach needs to explain away apparently substantive uses of the notion, such as 'science aims at the truth', or 'truth is a norm governing discourse'. Post-modern writing frequently advocates that we must abandon such norms, along with a discredited 'objective' conception of truth, perhaps, we can have the norms even when objectivity is problematic, since they can be framed without mention of truth: Science wants it to be so that whatever science holds that 'p', then 'p'. Discourse is to be regulated by the principle that it is wrong to assert 'p', when 'not-p'.
Something that tends of something in addition of content, or coming by way to justify such a position can very well be more that in addition to several reasons, as to bring in or adjoin of something might that there be more so as to a larger combination for us to consider the simplest formulation, is that 'real', assuming that it is right to demand something as one's own or one's due to its call for the challenge and maintain contentually justified. The demands adduced to forgo a defendable right of contend is a real or assumed placement to defend his greatest claim to fame. Claimed that expression of the attached adherently following the responsive quality values as explicated by the body of people who attaches them to another epically as disciplines, patrons or admirers, after al, to come after in time follows the succeeded succession to the proper lineage of the modelled composite of 'S is true' means the same as an induction or enactment into being its expression from something hided, latent or reserved to be educed to arouse the excogitated form of 'S'. Some philosophers dislike the ideas of sameness of meaning, and if this I disallowed, then the claim is that the two forms are equivalent in any sense of equivalence that matters. This is, it makes no difference whether people say 'Dogs bark' is True, or whether they say, 'dogs bark'. In the former representation of what they say of the sentence 'Dogs bark' is mentioned, but in the later it appears to be used, of the claim that the two are equivalent and needs careful formulation and defence. On the face of it someone might know that 'Dogs bark' is true without knowing what it means (for instance, if he kids in a list of acknowledged truths, although he does not understand English), and this is different from knowing that dogs bark. Disquotational theories are usually presented as versions of the 'redundancy theory of truth'.
The relationship between a set of premises and a conclusion when the conclusion follows from the premise, as several philosophers identify this with it being logically impossible that the premises should all be true, yet the conclusion false. Others are sufficiently impressed by the paradoxes of strict implication to look for a stranger relation, which would distinguish between valid and invalid arguments within the sphere of necessary propositions. The seraph for a strange notion is the field of relevance logic.
From a systematic theoretical point of view, we may imagine the process of evolution of an empirical science to be a continuous process of induction. Theories are evolved and are expressed in short compass as statements of as large number of individual observations in the form of empirical laws, from which the general laws can be ascertained by comparison. Regarded in this way, the development of a science bears some resemblance to the compilation of a classified catalogue. It is a purely empirical enterprise.
But this point of view by no means embraces the whole of the actual process, for it overlooks the important part played by intuition and deductive thought in the development of an exact science. As soon as a science has emerged from its initial stages, theoretical advances are no longer achieved merely by a process of arrangement. Guided by empirical data, the examiners develop a system of thought which, in general, it is built up logically from a small number of fundamental assumptions, the so-called axioms. We call such a system of thought a 'theory'. The theory finds the justification for its existence in the fact that it correlates a large number of single observations, and is just here that the 'truth' of the theory lies.
Corresponding to the same complex of empirical data, there may be several theories, which differ from one another to a considerable extent. But as regards the deductions from the theories which are capable of being tested, the agreement between the theories may be so complete, that it becomes difficult to find any deductions in which the theories differ from each other. As an example, a case of general interest is available in the province of biology, in the Darwinian theory of the development of species by selection in the struggle for existence, and in the theory of development which is based on the hypothesis of the hereditary transmission of acquired characters. The Origin of Species was principally successful in marshalling the evidence for evolution, than providing a convincing mechanism for genetic change. And Darwin himself remained open to the search for additional mechanisms, while also remaining convinced that natural selection was at the hart of it. It was only with the later discovery of the gene as the unit of inheritance that the synthesis known as 'neo-Darwinism' became the orthodox theory of evolution in the life sciences.
In the 19th century the attempt to base ethical reasoning o the presumed facts about evolution, the movement is particularly associated with the English philosopher of evolution Herbert Spencer (1820-1903), the premise is that later elements in an evolutionary path are better than earlier ones: The application of this principle then requires seeing western society, laissez-faire capitalism, or some other object of approval, as more evolved than more 'primitive' social forms. Neither the principle nor the applications command much respect. The version of evolutionary ethics called 'social Darwinism' emphasises the struggle for natural selection, and draws the conclusion that we should glorify and assist such struggles are usually by enhancing competition and aggressive relations between people in society or between evolution and ethics has been re-thought in the light of biological discoveries concerning altruism and kin-selection.
Once again, psychological attempts are found to establish a point by appropriate objective means, in that their evidences are well substantiated within the realm of evolutionary principles, in which a variety of higher mental functions may be adaptations, forced in response to selection pressures on the human populations through evolutionary time. Candidates for such theorizing include material and paternal motivations, capacities for love and friendship, the development of language as a signalling system cooperative and aggressive, our emotional repertoire, our moral and reactions, including the disposition to detect and punish those who cheat on agreements or who 'free-ride' on the work of others, our cognitive structures, and many others. Evolutionary psychology goes hand-in-hand with Neurophysiologic evidence about the underlying circuitry in the brain which subserves the psychological mechanisms it claims to identify. The approach was foreshadowed by Darwin himself, and William James, as well as the sociology of E.O. Wilson. The terms of use are applied, more or less aggressively, especially to explanations offered in socio-biology and evolutionary psychology.
Another assumption that is frequently used to legitimate the real existence of forces associated with the invisible hand in neoclassical economics derives from Darwin's view of natural selection as a regarded-threat, competing between atomized organisms in the struggle for survival. In natural selection as we now understand it, cooperation appears to exist in complementary relation to competition. Complementary relationships between such results are emergent self-regulating properties that are greater than the sum of parts and that serve to perpetuate the existence of the whole.
According to E.O Wilson, the 'human mind evolved to believe in the gods'' and people 'need a sacred narrative' to have a sense of higher purpose. Yet it is also clear that the unspoken 'gods'' in his view are merely human constructs and, therefore, there is no basis for dialogue between the world-view of science and religion. 'Science for its part', said Wilson, 'will test relentlessly every assumption about the human condition and in time uncover the bedrock of the moral and religious sentiment. The eventual result of the competition between each other will be the secularization of the human epic and of religion itself.
Man has come to the threshold of a state of consciousness, regarding his nature and his relationship to the Cosmos, in terms that reflect 'reality'. By using the processes of nature as metaphor, to describe the forces by which it operates upon and within Man, we come as close to describing 'reality' as we can within the limits of our comprehension. Men will be very uneven in their capacity for such understanding, which, naturally, differs for different ages and cultures, and develops and changes over the course of time. For these reasons it will always be necessary to use metaphor and myth to provide 'comprehensible' guides to living in this way. Man's imagination and intellect play vital roles on his survival and evolution.
Since so much of life both inside and outside the study is concerned with finding explanations of things, it would be desirable to have a concept of what counts as a good explanation from bad. Under the influence of 'logical positivist' approaches to the structure of science, it was felt that the criterion ought to be found in a definite logical relationship between the 'explanans' (that which does the explaining) and the explanandum (that which is to be explained). The approach culminated in the covering law model of explanation, or the view that an event is explained when it is subsumed under a law of nature, that is, its occurrence is deducible from the law plus a set of initial conditions. A law would itself be explained by being deduced from a higher-order or covering law, in the way that Johannes Kepler(or Keppler, 1571-1630), was by way of planetary motion that the laws were deducible from Newton's laws of motion. The covering law model may be adapted to include explanation by showing that something is probable, given a statistical law. Questions for the covering law model include querying for the covering laws are necessary to explanation (we explain whether everyday events without overtly citing laws): Querying whether they are sufficient (it may not explain an event just to say that it is an example of the kind of thing that always happens). And querying whether a purely logical relationship is adapted to capturing the requirements, which we make of explanations, and these may include, for instance, that we have a 'feel' for what is happening, or that the explanation proceeds in terms of things that are familiar to us or unsurprising, or that we can give a model of what is going on, and none of these notions is captured in a purely logical approach. Recent work, therefore, has tended to stress the contextual and pragmatic elements in requirements for explanation, so that what counts as good explanation given one set of concerns may not do so given another.
The argument to the best explanation is the view that once we can select the best of any in something in explanations of an event, then we are justified in accepting it, or even believing it. The principle needs qualification, since something it is unwise to ignore the antecedent improbability of a hypothesis which would explain the data better than others, e.g., the best explanation of a coin falling heads 530 times in 1,000 tosses might be that it is biassed to give a probability of heads of 0.53 but it might be more sensible to suppose that it is fair, or to suspend judgement.
In a philosophy of language is considered as the general attempt to understand the components of a working language, the relationship the understanding speaker has to its elements, and the relationship they bear to the world. The subject therefore embraces the traditional division of semiotic into syntax, semantics, and pragmatics. The philosophy of language thus mingles with the philosophy of mind, since it needs an account of what it is in our understanding that enables us to use language. It so mingles with the metaphysics of truth and the relationship between sign and object. Much as much is that the philosophy in the 20th century, has been informed by the belief that philosophy of language is the fundamental basis of all philosophical problems, in that language is the distinctive exercise of mind, and the distinctive way in which we give shape to metaphysical beliefs. Particular topics will include the problems of logical form, for which is the basis of the division between syntax and semantics, as well as problems of understanding the number and nature of specifically semantic relationships such as meaning, reference, predication, and quantification. Pragmatics includes that of speech acts, while problems of rule following and the indeterminacy of translation infect philosophies of both pragmatics and semantics.
On this conception, to understand a sentence is to know its truth-conditions, and, yet, in a distinctive way the conception has remained central that those who offer opposing theories characteristically define their position by reference to it. The Conceptions of meaning s truth-conditions needs not and ought not to be advanced for being in itself as complete account of meaning. For instance, one who understands a language must have some idea of the range of speech acts contextually performed by the various types of the sentence in the language, and must have some idea of the insufficiencies of various kinds of speech acts. The claim of the theorist of truth-conditions should rather be targeted on the notion of content: If indicative sentences differ in what they strictly and literally say, then this difference is fully accounted for by the difference in the truth-conditions.
The meaning of a complex expression is a function of the meaning of its constituent. This is just as a sentence of what it is for an expression to be semantically complex. It is one of the initial attractions of the conception of meaning truth-conditions that it permits a smooth and satisfying account of the way in which the meaning of s complex expression is a function of the meaning of its constituents. On the truth-conditional conception, to give the meaning of an expression is to state the contribution it makes to the truth-conditions of sentences in which it occurs. For singular terms - proper names, indexical, and certain pronouns - this is done by stating the reference of the terms in question. For predicates, it is done either by stating the conditions under which the predicate is true of arbitrary objects, or by stating the conditions under which arbitrary atomic sentences containing it is true. The meaning of a sentence-forming operator is given by stating its contribution to the truth-conditions of as complex sentence, as a function of the semantic values of the sentences on which it operates.
The theorist of truth conditions should insist that not every true statement about the reference of an expression is fit to be an axiom in a meaning-giving theory of truth for a language, such is the axiom: 'London' refers to the city in which there was a huge fire in 1666, is a true statement about the reference of 'London'. It is a consequent of a theory which substitutes this axiom for no different a term than of our simple truth theory that 'London is beautiful' is true if and only if the city in which there was a huge fire in 1666 is beautiful. Since a psychological subject can understand, the given name to 'London' without knowing that last-mentioned truth condition, this replacement axiom is not fit to be an axiom in a meaning-specifying truth theory. It is, of course, incumbent on a theorised meaning of truth conditions, to state in a way which does not presuppose any previous, non-truth conditional conception of meaning
Among the many challenges facing the theorist of truth conditions, two are particularly salient and fundamental. First, the theorist has to answer the charge of triviality or vacuity; second, the theorist must offer an account of what it is for a person's language to be truly describable by as semantic theory containing a given semantic axiom.
Since the content of a claim that the sentence, 'Paris is beautiful' is the true amount under which there will be no more than the claim that Paris is beautiful, we can trivially describers understanding a sentence, if we wish, as knowing its truth-conditions, but this gives us no substantive account of understanding whatsoever. Something other than the grasp of truth conditions must provide the substantive account. The charge rests upon what has been called the redundancy theory of truth, the theory which, somewhat more discriminatingly. Horwich calls the minimal theory of truth. It’s conceptual representation that the concept of truth is exhausted by the fact that it conforms to the equivalence principle, the principle that for any proposition 'p', it is true that 'p' if and only if 'p'. Many different philosophical theories of truth will, with suitable qualifications, accept that equivalence principle. The distinguishing feature of the minimal theory is its claim that the equivalence principle exhausts the notion of truth. It is now widely accepted, both by opponents and supporters of truth conditional theories of meaning, that it is inconsistent to accept both minimal theory of truth and a truth conditional account of meaning. If the claim that a sentence 'Paris is beautiful' is true is exhausted by its equivalence to the claim that Paris is beautiful, it is circular to try of its truth conditions. The minimal theory of truth has been endorsed by the Cambridge mathematician and philosopher Plumpton Ramsey (1903-30), and the English philosopher Jules Ayer, the later Wittgenstein, Quine, Strawson and Horwich and - confusing and inconsistently if this article is correct - Frége himself. But is the minimal theory correct?
The minimal theory treats instances of the equivalence principle as definitional of truth for a given sentence, but in fact, it seems that each instance of the equivalence principle can itself be explained. The truth from which such an instance as, 'London is beautiful' is true if and only if London is beautiful. This would be a pseudo-explanation if the fact that 'London' refers to London consists in part in the fact that 'London is beautiful' has the truth-condition it does. But it is very implausible, it is, after all, possible for apprehending and for its understanding of the name 'London' without understanding the predicate 'is beautiful'.
Sometimes, however, the counterfactual conditional is known as subjunctive conditionals, insofar as a counterfactual conditional is a conditional of the form if 'p' were to happen 'q' would, or if 'p' were to have happened 'q' would have happened, where the supposition of 'p' is contrary to the known fact that 'not-p'. Such assertions are nevertheless, useful 'if you broke the bone, the X-ray would have looked different', or 'if the reactor was to fail, this mechanism would click in' are important truths, even when we know that the bone is not broken or are certain that the reactor will not fail. It is arguably distinctive of laws of nature that yield counter-factual ('if the metal were to be heated, it would expand'), whereas accidentally true generalizations may not. It is clear that counter-factual cannot be represented by the material implication of the propositional calculus, since that conditionals come out true whenever 'p' is false, so there would be no division between true and false counter-factual.
Although the subjunctive form indicates the counterfactual, in many contexts it does not seem to matter whether we use a subjunctive form, or a simple conditional form: 'If you run out of water, you will be in trouble' seems equivalent to 'if you were to run out of water, you would be in trouble', in other contexts there is a big difference: 'If Oswald did not kill Kennedy, someone else did' is clearly true, whereas 'if Oswald had not killed Kennedy, someone would have' is most probably false.
The best-known modern treatment of counter-factual is that of David Lewis, which evaluates them as true or false according to whether 'q' is true in the 'most similar' possible worlds to ours in which 'p' is true. The similarity-ranking this approach is needed to prove of the controversial, particularly since it may need to presuppose some notion of the same laws of nature, whereas art of the interest in counterfactual is that they promise to illuminate that notion. There is an expanding force of awareness that the classification of conditionals is an extremely tricky business, and categorizing them as counterfactual or not that it is of limited use.
The pronouncing of any conditional, preposition of the form 'if p then q', the condition hypothesizes, 'p'. It's called the antecedent of the conditional, and 'q' the consequent. Various kinds of conditional have been distinguished. Weaken in that of material implication, merely telling us that with 'not-p' or 'q', stronger conditionals include elements of modality, corresponding to the thought that if 'p' is true then 'q' must be true. Ordinary language is very flexible in its use of the conditional form, and there is controversy whether, yielding different kinds of conditionals with different meanings, or pragmatically, in which case there should be one basic meaning which case there should be one basic meaning, with surface differences arising from other implicatures.
Passively, there are many forms of reliabilism. Just as there are many forms of 'Foundationalism' and 'coherence'. How is reliabilism related to these other two theories of justification? We usually regard it as a rival, and this is aptly so, insofar as Foundationalism and coherentism traditionally focussed on purely evidential relations than psychological processes, but we might also offer reliabilism as a deeper-level theory, subsuming some precepts of either Foundationalism or coherentism. Foundationalism says that there are 'basic' beliefs, which acquire justification without dependence on inference; reliabilism might rationalize this indicating that reliable non-inferential processes have formed the basic beliefs. Coherence stresses the primary of systematic in all doxastic decision-making. Reliabilism might rationalize this by pointing to increases in reliability that accrue from systematic consequently, reliabilism could complement Foundationalism and coherence than completed with them.
These examples make it seem likely that, if there is a criterion for what makes an alternate situation relevant that will save Goldman's claim about local reliability and knowledge. Will did not be simple. The interesting thesis that counts as a causal theory of justification, in the making of 'causal theory' intended for the belief as it is justified in case it was produced by a type of process that is 'globally' reliable, that is, its propensity to produce true beliefs that can be defined, to an acceptable approximation, as the proportion of the beliefs it produces, or would produce where it used as much as opportunity allows, that is true is sufficiently reasonable. We have advanced variations of this view for both knowledge and justified belief, its first formulation of a reliability account of knowing appeared in the notation from F.P.Ramsey (1903-30). The theory of probability, he was the first to show how a 'personality theory' could be progressively advanced from a lower or simpler to a higher or more complex form, as developing to come to have usually gradual acquirements, only based on a precise behaviour al notion of preference and expectation. In the philosophy of language, much of Ramsey's work was directed at saving classical mathematics from 'intuitionism', or what he called the 'Bolshevik harassments of Brouwer and Weyl. In the theory of probability he was the first to show how we could develop some personalist's theory, based on precise behavioural notation of preference and expectation. In the philosophy of language, Ramsey was one of the first thinkers, which he combined with radical views of the function of many kinds of a proposition. Neither generalizations, nor causal propositions, nor those treating probability or ethics, describe facts, but each has a different specific function in our intellectual economy. Ramsey was one of the earliest commentators on the early work of Wittgenstein and his continuing friendship that led to Wittgenstein's return to Cambridge and to philosophy in 1929.
Ramsey's sentence theory is the sentence generated by taking all the sentences affirmed in a scientific theory that use some term, e.g., 'quark'. Replacing the term by a variable, and existentially quantifying into the result, instead of saying that quarks have such-and-such properties, the Ramsey sentence says that there is something that has those properties. If we repeat the process for all of a group of the theoretical terms, the sentence gives the 'topic-neutral' structure of the theory, but removes any implication that we know what the term so treated prove competent. It leaves open the possibility of identifying the theoretical item with whatever, but it is that best fits the description provided, virtually, all theories of knowledge. Of course, share an externalist component in requiring truth as a condition for known in. Reliabilism goes further, however, in trying to capture additional conditions for knowledge by ways of a nomic, counterfactual or similar 'external' relations between belief and truth, closely allied to the nomic sufficiency account of knowledge. The core of this approach is that X's belief that 'p' qualifies as knowledge just in case 'X' believes 'p', because of reasons that would not obtain unless 'p's' being true, or because of a process or method that would not yield belief in 'p' if 'p' were not true. An enemy example, 'X' would not have its current reasons for believing there is a telephone before it. Or consigned to not come to believe this in the ways it does, thus, there is a counterfactual reliable guarantor of the belief's being true. Determined to and the facts of counterfactual approach say that 'X' knows that 'p' only if there is no 'relevant alternative' situation in which 'p' is false but 'X' would still believe that a proposition 'p'; must be sufficient to eliminate all the alternatives too 'p' where an alternative to a proposition 'p' is a proposition incompatible with 'p?'. That I, one's justification or evidence for 'p' must be sufficient for one to know that every alternative too 'p' is false. This element of our evolving thinking, sceptical arguments have exploited about which knowledge. These arguments call our attentions to alternatives that our evidence sustains itself with no elimination. The sceptic inquires to how we know that we are not seeing a cleverly disguised mule. While we do have some evidence against the likelihood of such as deception, intuitively knowing that we are not so deceived is not strong enough for 'us'. By pointing out alternate but hidden points of nature, in that we cannot eliminate, and others with more general application, as dreams, hallucinations, etc. The sceptic appears to show that every alternative is seldom. If ever, satisfied.
All the same, and without a problem, is noted by the distinction between the 'in itself' and the; for itself' originated in the Kantian logical and epistemological distinction between a thing as it is in itself, and that thing as an appearance, or as it is for us. For Kant, the thing in itself is the thing as it is intrinsically, that is, the character of the thing apart from any relations in which it happens to stand. The thing for which, or as an appearance, is the thing in so far as it stands in relation to our cognitive faculties and other objects. 'Now a thing in itself cannot be known through mere relations: and we may therefore conclude that since outer sense gives us nothing but mere relations, this sense can contain in its representation only the relation of an object to the subject, and not the inner properties of the object in itself'. Kant applies this same distinction to the subject's cognition of itself. Since the subject can know itself only in so far as it can intuit itself, and it can intuit itself only in terms of temporal relations, and thus as it is related to its own self, it represents itself 'as it appears to itself, not as it is'. Thus, the distinction between what the subject is in itself and hat it is for itself arises in Kant in so far as the distinction between what an object is in itself and what it is for a knower is applied to the subject's own knowledge of itself.
Hegel (1770-1831) begins the transition of the epistemological distinct ion between what the subject is in itself and what it is for itself into an ontological distinction. Since, for Hegel, what is, s it is in fact it in itself, necessarily involves relation, the Kantian distinction must be transformed. Taking his cue from the fact that, even for Kant, what the subject is in fact it in itself involves a relation to itself, or self-consciousness. Hegel suggests that the cognition of an entity in terms of such relations or self-relations do not preclude knowledge of the thing itself. Rather, what an entity is intrinsically, or in itself, is best understood in terms of the potentiality of that thing to enter specific explicit relations with it. And, just as for consciousness to be explicitly itself is for it to be for itself by being in relation to itself, i.e., to be explicitly self-conscious, for-itself of any entity is that entity in so far as it is actually related to itself. The distinction between the entity in itself and the entity for itself is thus taken to apply to every entity, and not only to the subject. For example, the seed of a plant is that plant in itself or implicitly, while the mature plant which involves actual relation among the plant's various organs is the plant 'for itself'. In Hegel, then, the in itself/for itself distinction becomes universalized, in is applied to all entities, and not merely to conscious entities. In addition, the distinction takes on an ontological dimension. While the seed and the mature plant are one and the same entity, being in itself of the plan, or the plant as potential adult, in that an ontologically distinct commonality is in for itself on the plant, or the actually existing mature organism. At the same time, the distinction retains an epistemological dimension in Hegel, although its import is quite different from that of the Kantian distinction. To know a thing, it is necessary to know both the actual explicit self-relations which mark the thing (the being for itself of the thing), and the inherent simpler principle of these relations, or the being in itself of the thing. Real knowledge, for Hegel, thus consists in knowledge of the thing as it is in and for itself.
Sartre's distinction between being in itself and being for itself, which is an entirely ontological distinction with minimal epistemological import, is descended from the Hegelian distinction. Sartre distinguishes between what it is for consciousness to be, i.e., being for itself, and the being of the transcendent being which is intended by consciousness, i.e., being in itself. What is it for consciousness to be, being for itself, is marked by self relation? Sartre posits a 'Pre-reflective Cogito', such that every consciousness of '?' necessarily involves a 'non-positional' consciousness of the consciousness of '?'. While in Kant every subject is both in itself, i.e., as it is apart from its relations, and for itself in so far as it is related to itself, and for itself in so far as it is related to itself by appearing to itself, and in Hegel every entity can be considered as both 'in itself' and 'for itself', in Sartre, to be self-related or for itself is the distinctive ontological mark of consciousness, while to lack relations or to be in itself is the distinctive e ontological mark of non-conscious entities.
This conclusion conflicts with another strand in our thinking about knowledge, in that we know many things. Thus, there is a tension in our ordinary thinking about knowledge -. We believe that knowledge is, in the sense indicated, an absolute concept and yet, we also believe that there are many instances of that concept.
If one finds absoluteness to be too central a component of our concept of knowledge to be relinquished, one could argue from the absolute character of knowledge to a sceptic conclusion (Unger, 1975). Most philosophers, however, have taken the other course, choosing to respond to the conflict by giving up, perhaps reluctantly, the absolute criterion. This latter response holds as sacrosanct our commonsense belief that we know many things (Pollock, 1979 and Chisholm, 1977). Each approach is subject to the criticism that it preserves one aspect of our ordinary thinking about knowledge at the expense of denying another. We can view the theory of relevant alternatives as an attempt to provide a more satisfactory response to this tension in our thinking about knowledge. It attempts to characterize knowledge in a way that preserves both our belief that knowledge is an absolute concept and our belief that we have knowledge.
This approach to the theory of knowledge that sees an important connection between the growth of knowledge and biological evolution an evolutionary epistemologist claims that the development of human knowledge processed through some natural selection process, the best example of which is Darwin's theory of biological natural selection. There is a widespread misconception that evolution proceeds according to some plan or direct, put it has neither, and the role of chance ensures that its future course will be unpredictable. Random variations in individual organisms create tiny differences in their Darwinian fitness. Some individuals have more offspring's than others, and the characteristics that increased their fitness thereby become more prevalent in future generations. Once upon a time, at least a mutation occurred in a human population in tropical Africa that changed the hemoglobin molecule in a way that provided resistance to malaria. This enormous advantage caused the new gene to spread; with the unfortunate consequence that sickle-cell anaemia came to exist.
When proximate and evolutionary explanations are carefully distinguished, many questions in biology make more sense. A proximate explanation describes a trait - its anatomy, physiology, and biochemistry, as well as its development from the genetic instructions provided by a bit of DNA in the fertilized egg to the adult individual. An evolutionary explanation is about why DNA specifies that trait in the first place and why has DNA that encodes for one kind of structure and not some other. Proximate and evolutionary explanations are not alternatives, but both are needed to understand every trait. A proximate explanation for the external ear would incorporate of its arteries and nerves, and how it develops from the embryo to the adult form. Even if we know this, however, we still need an evolutionary explanation of how its structure gives creatures with ears an advantage, why those that lack the structure shaped by selection to give the ear its current form. To take another example, a proximate explanation of taste buds describes their structure and chemistry, how they detect salt, sweet, sour, and bitter, and how they transform this information into impulses that travel via neurons to the brain. An evolutionary explanation of taste buds shows why they detect saltiness, acidity, sweetness and bitterness instead of other chemical characteristics, and how the capacities detect these characteristics help, and cope with life.
Chance can influence the outcome at each stage: First, in the creation of genetic mutation, second, in whether the bearer lives long enough to show its effects, thirdly, in chance events that influence the individual's actual reproductive success, and fourth, in whether a gene even if favoured in one generation, is, happenstance, eliminated in the next, and finally in the many unpredictable environmental changes that will undoubtedly occur in the history of any group of organisms. As Harvard biologist Stephen Jay Gould has so vividly expressed that process over again, the outcome would surely be different. Not only might there not be humans, there might not even be anything like mammals.
We will often emphasis the elegance of traits shaped by natural selection, but the common idea that nature creates perfection needs to be analysed carefully. The extent for which evolution obtainably achieves perfection depends on the enacting fitness for which Darwin speaks in terms of their survival and their fittest are most likely as perfect than the non-surviving species, only, that it enables us to know exactly what you mean. If in what you mean, 'Does natural selection always takes the best path for the long-term welfare of a species?' The answer is no. That would require adaptation by group selection, and this is, unlikely. If you mean 'Does natural selection creates every adaptation that would be valuable?' The answer again, is no. For instance, some kinds of South American monkeys can grasp branches with their tails. The trick would surely also be useful to some African species, but, simply because of bad luck, none have it. Some combination of circumstances started some ancestral South American monkeys using their tails in ways that ultimately led to an ability to grab onto branches, while no such development took place in Africa. Mere usefulness of a trait does not necessitate it mean that will evolve.
This is an approach to the theory of knowledge that sees an important connection between the growth of knowledge and biological evolution. An evolutionary epistemologist claims that the development of human knowledge proceeds through some natural selection process, the best example of which is Darwin's theory of biological natural selection. The three major components of the model of natural selection are variation selection and retention. According to Darwin's theory of natural selection, variations are not pre-designed to perform certain functions. Rather, these variations that perform useful functions are selected. While those that suffice on doing nothing are not selected but, nevertheless, such selections are responsible for the appearance that specific variations built upon intentionally do really occur. In the modern theory of evolution, genetic mutations provide the blind variations ( blind in the sense that variations are not influenced by the effects they would have, - the likelihood of a mutation is not correlated with the benefits or liabilities that mutation would confer on the organism), the environment provides the filter of selection, and reproduction provides the retention. It is achieved because those organisms with features that make them less adapted for survival do not survive about other organisms in the environment that have features that are better adapted. Evolutionary epistemology applies this blind variation and selective retention model to the growth of scientific knowledge and to human thought processes in general.
The parallel between biological evolutions and conceptual or we can see 'epistemic' evolution as either literal or analogical. The literal version of evolutionary epistemological biological evolution as the main cause of the growth of knowledge stemmed from this view, called the 'evolution of cognitive mechanic programs', by Bradie (1986) and the 'Darwinian approach to epistemology' by Ruse (1986), that growth of knowledge occurs through blind variation and selective retention because biological natural selection itself is the cause of epistemic variation and selection. The most plausible version of the literal view does not hold that all human beliefs are innate but rather than the mental mechanisms that guide the acquisition of non-innate beliefs are themselves innately and the result of biological natural selection. Ruses (1986) repossess to resume of the insistence of an interlingual rendition of literal evolutionary epistemology that he links to sociology.
Determining the value upon innate ideas can take the path to consider as these have been variously defined by philosophers either as ideas consciously present to the mind priori to sense experience (the non-dispositional sense), or as ideas which we have an innate disposition to form, though we need to be actually aware of them at a particular r time, e.g., as babies - the dispositional sense. Understood in either way they were invoked to account for our recognition of certain verification, such as those of mathematics, or to justify certain moral and religious clams which were held to b capable of being know by introspection of our innate ideas. Examples of such supposed truths might include 'murder is wrong' or 'God exists'.
One difficulty with the doctrine is that it is sometimes formulated as one about concepts or ideas which are held to be innate and at other times one about a source of propositional knowledge, in so far as concepts are taken to be innate the doctrine relates primarily to claims about meaning: Our idea of God, for example, is taken as a source for the meaning of the word God. When innate ideas are understood propositionally, their supposed innateness is taken an evidence for the truth. This latter thesis clearly rests on the assumption that innate propositions have an unimpeachable source, usually taken to be God, but then any appeal to innate ideas to justify the existence of God is circular. Despite such difficulties the doctrine of innate ideas had a long and influential history until the eighteenth century and the concept has in recent decades been revitalized through its employment in Noam Chomsky's influential account of the mind's linguistic capacities.
The attraction of the theory has been felt strongly by those philosophers who have been unable to give an alternative account of our capacity to recognize that some propositions are certainly true where that recognition cannot be justified solely o the basis of an appeal to sense experiences. Thus Plato argued that, for example, recognition of mathematical truths could only be explained on the assumption of some form of recollection, in Plato, the recollection of knowledge, possibly obtained in a previous stat e of existence e draws its topic as most famously broached in the dialogue “Meno,” and the doctrine is one attemptive account for the 'innate' unlearned character of knowledge of first principles. Since there was no plausible post-natal source the recollection must refer of a pre-natal acquisition of knowledge. Thus understood, the doctrine of innate ideas supported the views that there were importantly gradatorially innate human beings and it was this sense which hindered their proper apprehension.
The ascetic implications of the doctrine were important in Christian philosophy throughout the Middle Ages and scholastic teaching until its displacement by Locke' philosophy in the eighteenth century. It had in the meantime acquired modern expression in the philosophy of Descartes who argued that we can come to know certain important truths before we have any empirical knowledge at all. Our idea of God must necessarily exist, is Descartes held, logically independent of sense experience. In England the Cambridge Plantonists such as Henry Moore and Ralph Cudworth added considerable support.
Locke's rejection of innate ideas and his alternative empiricist account was powerful enough to displace the doctrine from philosophy almost totally. Leibniz, in his critique of Locke, attempted to defend it with a sophisticated disposition version of theory, but it attracted few followers.
The empiricist alternative to innate ideas as an explanation of the certainty of propositions in the direction of construing with necessary truths as analytic, justly be for Kant's refinement of the classification of propositions with the fourfold analytic/synthetic distention and deductive/inductive did nothing to encourage a return to their innate idea's doctrine, which slipped from view. The doctrine may fruitfully be understood as the genesis of confusion between explaining the genesis of ideas or concepts and the basis for regarding some propositions as necessarily true.
Chomsky's revival of the term in connection with his account of the spoken exchange acquisition has once more made the issue topical. He claims that the principles of language and 'natural logic' are known unconsciously and is a precondition for language acquisition. But for his purposes innate ideas must be taken in a strong dispositional sense - so strong that it is far from clear that Chomsky's claims are as in direct conflict, and make unclear in mind or purpose, as with empiricists accounts of valuation, some (including Chomsky) have supposed. Willard van Orman Quine (1808-2000), for example, sees no disaccording with his own version of empirical behaviourism, in which sees the typical of an earlier time and often replaced by something more modern or fashionable converse [in] views upon the meaning of determining what a thing should be, as each generation has its own standards of mutuality.
Locke' accounts of analytic propositions was, that everything that a succinct account of analyticity should be (Locke, 1924). He distinguishes two kinds of analytic propositions, identity propositions for which 'we affirm the said term of itself', e.g., 'Roses are roses' and predicative propositions in which 'a part of the complex idea is predicated of the name of the whole', e.g., 'Roses are flowers'. Locke calls such sentences 'trifling' because a speaker who uses them 'trifling with words'. A synthetic sentence, in contrast, such as a mathematical theorem, that state of real truth and presents its instructive parallel's of real knowledge'. Correspondingly, Locke distinguishes both kinds of 'necessary consequences', analytic entailments where validity depends on the literal containment of the conclusion in the premise and synthetic entailment where it does not. John Locke (1632-1704) did not originate this concept-containment notion of analyticity. It is discussed by Arnaud and Nicole, and it is safe to say that it has been around for a very long time.
All the same, the analogical version of evolutionary epistemology, called the 'evolution of theory's program', by Bradie (1986). The 'Spenserians approach' (after the nineteenth century philosopher Herbert Spencer) by Ruse (1986), a process analogous to biological natural selection has governed the development of human knowledge, rather than by an instance of the mechanism itself. This version of evolutionary epistemology, introduced and elaborated by Donald Campbell (1974) and Karl Popper, sees the [partial] fit between theories and the world as explained by a mental process of trial and error known as epistemic natural selection.
We have usually taken both versions of evolutionary epistemology to be types of naturalized epistemology, because both take some empirical facts as a starting point for their epistemological project. The literal version of evolutionary epistemology begins by accepting evolutionary theory and a materialist approach to the mind and, from these, constructs an account of knowledge and its developments. By contrast, the analogical version does not require the truth of biological evolution: It simply draws on biological evolution as a source for the model of natural selection. For this version of evolutionary epistemology to be true, the model of natural selection need only apply to the growth of knowledge, not to the origin and development of species. Savagery put, evolutionary epistemology of the analogical sort could still be true even if creationism is the correct theory of the origin of species.
Although they do not begin by assuming evolutionary theory, most analogical evolutionary epistemologists are naturalized epistemologists as well, their empirical assumptions, least of mention, implicitly come from psychology and cognitive science, not evolutionary theory. Sometimes, however, evolutionary epistemology is characterized in a seemingly non-naturalistic fashion. (Campbell 1974) says that 'if one is expanding knowledge beyond what one knows, one has no choice but to explore without the benefit of wisdom', i.e., blindly. This, Campbell admits, makes evolutionary epistemology close to being a tautology (and so not naturalistic). Evolutionary epistemology does assert the analytic claim that when expanding one's knowledge beyond what one knows, one must processed to something that is already known, but, more interestingly, it also makes the synthetic claim that when expanding one's knowledge beyond what one knows, one must proceed by blind variation and selective retention. This claim is synthetic because we can empirically falsify it. The central claim of evolutionary epistemology is synthetic, not analytic, but if the central contradictory of which they are not, then Campbell is right that evolutionary epistemology does have the analytic feature he mentions, but he is wrong to think that this is a distinguishing feature, since any plausible epistemology has the same analytic feature.
Two extra-ordinary issues lie to awaken the literature that involves questions about 'realism', i.e., what metaphysical commitment does an evolutionary epistemologist have to make? (Progress, i.e., according to evolutionary epistemology, does knowledge develop toward a goal?) With respect to realism, many evolutionary epistemologists endorse that is called 'hypothetical realism', a view that combines a version of epistemological 'scepticism' and tentative acceptance of metaphysical realism. With respect to progress, the problem is that biological evolution is not goal-directed, but the growth of human knowledge is. Campbell (1974) worries about the potential dis-analogy here but is willing to bite the stone of conscience and admit that epistemic evolution progress toward a goal (truth) while biological evolution does not. Some have argued that evolutionary epistemologists must give up the 'truth-topic' sense of progress because a natural selection model is in non-teleological in essence alternatively, following Kuhn (1970), and embraced along with evolutionary epistemology.
Among the most frequent and serious criticisms levelled against evolutionary epistemology is that the analogical version of the view is false because epistemic variation is not blind are to argue that, however, that this objection fails because, while epistemic variation is not random, its constraints come from heuristics that, for the most part, are selective retention. Further, Stein and Lipton argue that lunatics are analogous to biological pre-adaptations, evolutionary pre-biological pre-adaptations, evolutionary cursors, such as a half-wing, a precursor to a wing, which have some function other than the function of their discountable structures: The function of descendability may result in the function of their descendable character embodied to its structural foundations, is that of the guideline of epistemic variation is, on this view, not the source of dis-analogy, but the source of a more articulated account of the analogy.
Many evolutionary epistemologists try to combine the literal and the analogical versions, saying that those beliefs and cognitive mechanisms, which are innate results from natural selection of the biological sort and those that are innate results from natural selection of the epistemic sort. This is reasonable as long as the two parts of this hybrid view are kept distinct. An analogical version of evolutionary epistemology with biological variation as its only source of blindness would be a null theory: This would be the case if all our beliefs are innate or if our non-innate beliefs are not the result of blind variation. An appeal to the legitimate way to produce a hybrid version of evolutionary epistemology since doing so trivializes the theory. For similar reasons, such an appeal will not save an analogical version of evolutionary epistemology from arguments to the effect that epistemic variation is blind.
Although it is a new approach to theory of knowledge, evolutionary epistemology has attracted much attention, primarily because it represents a serious attempt to flesh out a naturalized epistemology by drawing on several disciplines. In science is used for understanding the nature and development of knowledge, then evolutionary theory is among the disciplines worth a look. Insofar as evolutionary epistemology looks there, it is an interesting and potentially fruitful epistemological programmed.
What makes a belief justified and what makes true belief knowledge? Thinking that whether a belief deserves one of these appraisals is natural depends on what caused such subjectivity to have the belief. In recent decades many epistemologists have pursued this plausible idea with a variety of specific proposals. Some causal theories of knowledge have it that a true belief that 'p' is knowledge just in case it has the right causal connection to the fact that 'p'. They can apply such a criterion only to cases where the fact that 'p' is a sort that can enter intuit causal relations, as this seems to exclude mathematically and other necessary facts and perhaps any fact expressed by a universal generalization, and proponents of this sort of criterion have usually supposed that it is limited to perceptual representations where knowledge of particular facts about subjects' environments.
For example, Armstrong (1973) initially proposed something which is proposed to another for consideration, as a set before the mind for consideration, as to put forth an intended purpose. That a belief to carry a one's affairs independently and self-sufficiently often under difficult circumstances progress for oneself and makes do and stand on one's own formalities in the transitional form 'This [perceived] objects is 'F' is [non-inferential] knowledge if and only if the belief is a completely reliable sign that the perceived object is 'F', that is, the fact that the object is 'F' contributed to causing the belief and its doing so depended on properties of the believer such that the laws of nature dictated that, for any subject, and the perceived objective 'y', if 'p' had those properties and believed that 'y' is 'F', then 'y' is 'F'. Offers a rather similar account, in terms of the belief's being caused by a signal received by the perceiver that carries the information that the object is 'F'.
This sort of condition fails, however, to be sufficiently for non-inferential perceptivity, for knowledge is accountable for its compatibility with the belief's being unjustified, and an unjustified belief cannot be knowledge. The view that a belief acquires favourable epistemic status by having some kind of reliable linkage to the truth, seems by accountabilities that they have variations of this view which has been advanced for both knowledge and justified belief. The first formulation of a reliable account of knowing notably appeared as marked and noted and accredited to F. P. Ramsey (1903-30), whereby much of Ramsey's work was directed at saving classical mathematics from 'intuitionism', or what he called the 'Bolshevik menace of Brouwer and Weyl'. In the theory of probability he was the first to develop, based on precise behavioural nations of preference and expectation. In the philosophy of language, Ramsey was one of the first thinkers to accept a 'redundancy theory of truth', which he combined with radical views of the function of many kinds of propositions. Neither generalizations, nor causal positions, nor those treating probability or ethics, described facts, but each have a different specific function in our intellectual economy. Additionally, Ramsey, who said that an impression of belief was knowledge if it were true, certain and obtained by a reliable process. P. Unger (1968) suggested that 'S' knows that 'p' just in case it is of at all accidental that 'S' is right about its being the case that drew an analogy between a thermometer that reliably indicates the temperature and a belief interaction of reliability that indicates the truth. Armstrong said that a non-inferential belief qualified as knowledge if the belief has properties that are nominally sufficient for its truth, i.e., guarantees its truth via laws of nature.
They standardly classify reliabilism as an 'externaturalist' theory because it invokes some truth-linked factor, and truth is 'eternal' to the believer the main argument for externalism derives from the philosophy of language, more specifically, from the various phenomena pertaining to natural kind terms, indexicals, etc., that motivate the views that have come to be known as direct reference' theories. Such phenomena seem, at least to show that the belief or thought content that can be properly attributed to a person is dependent on facts about his environment, i.e., whether he is on Earth or Twin Earth, what in fact he is pointing at, the classificatory criteria employed by the experts in his social group, etc. -. Not just on what is going on internally in his mind or brain (Putnam, 175 and Burge, 1979.) Virtually all theories of knowledge, of course, share an externalist component in requiring truth as a condition for knowing. Reliabilism goes further, however, in trying to capture additional conditions for knowledge by means of a nomic, counterfactual or other such 'external' relations between 'belief' and 'truth'.
The most influential counterexample to reliabilism is the demon-world and the clairvoyance examples. The demon-world example challenges the necessity of the reliability requirement, in that a possible world in which an evil demon creates deceptive visual experience, the process of vision is not reliable. Still, the visually formed beliefs in this world are intuitively justified. The clairvoyance example challenges the sufficiency of reliability. Suppose a cognitive agent possesses a reliable clairvoyance power, but has no evidence for or against his possessing such a power. Intuitively, his clairvoyantly formed beliefs are unjustifiably unreasoned, but reliabilism declares them justified.
Another form of reliabilism, - 'normal worlds', reliabilism, answers to the range problem differently, and treats the demon-world problem in the same fashionable manner, and so permitting a 'normal world', as one that is consistent with our general beliefs about the actual world. Normal-worlds reliabilism says that a belief, in any possible world is justified just in case its generating processes have high truth ratios in normal worlds. This resolves the demon-world problem because the relevant truth ratio of the visual process is not its truth ratio in the demon world itself, but its ratio in normal worlds. Since this ratio is presumably high, visually formed beliefs in the demon world turn out to be justified.
Yet, a different version of reliabilism attempts to meet the demon-world and clairvoyance problems without recourse to the questionable notion of 'normal worlds'. Consider Sosa's (1992) suggestion that justified beliefs is belief acquired through 'intellectual virtues', and not through intellectual 'vices', whereby virtues are reliable cognitive faculties or processes. The task is to explain how epistemic evaluators have used the notion of indelible virtues, and vices, to arrive at their judgments, especially in the problematic cases. Goldman (1992) proposes a two-stage reconstruction of an evaluator's activity. The first stage is a reliability-based acquisition of a 'list' of virtues and vices. The second stage is application of this list to queried cases. Determining has executed the second stage whether processes in the queried cases resemble virtues or vices. We have classified visual beliefs in the demon world as justified because visual belief formation is one of the virtues. Clairvoyance formed, beliefs are classified as unjustified because clairvoyance resembles scientifically suspect processes that the evaluator represents as vices, e.g., mental telepathy, ESP, and so forth
A philosophy of meaning and truth, for which it is especially associated with the American philosopher of science and of language (1839-1914), and the American psychologist philosopher William James (1842-1910), Wherefore the study in Pragmatism is given to various formulations by both writers, but the core is the belief that the meaning of a doctrine is the same as the practical effects of adapting it. Peirce interpreted of theocratical sentences ids only that of a corresponding practical maxim (telling us what to do in some circumstance). In James the position issues in a theory of truth, notoriously allowing that belief, including for examples, belief in God, are the widest sense of the works satisfactorily in the widest sense of the word. On James's view almost any belief might be respectable, and even true, but working with true beliefs is not a simple matter for James. The apparent subjectivist consequences of this were wildly assailed by Russell (1872-1970), Moore (1873-1958), and others in the early years of the 20th-century. This led to a division within pragmatism between those such as the American educator John Dewey (1859-1952), whose humanistic conception of practice remains inspired by science, and the more idealistic route that especially by the English writer F.C.S. Schiller (1864-1937), embracing the doctrine that our cognitive efforts and human needs actually transform the reality that we seek to describe. James often writes as if he sympathizes with this development. For instance, in The Meaning of Truth (1909), he considers the hypothesis that other people have no minds (dramatized in the sexist idea of an 'automatic sweetheart' or female zombie) and remarks' that the hypothesis would not work because it would not satisfy our egoistic craving for the recognition and admiration of others, these implications that make it true that the other persons have minds in the disturbing part.
Modern pragmatists such as the American philosopher and critic Richard Rorty (1931-) and some writings of the philosopher Hilary Putnam (1925-) who has usually tried to dispense with an account of truth and concentrate, as perhaps James should have done, upon the nature of belief and its relations with human attitude, emotion, and need. The driving motivation of pragmatism is the idea that belief in the truth on the one hand must have a close connection with success in action on the other. One way of cementing the connection is found in the idea that natural selection must have adapted us to be cognitive creatures because beliefs have effects, as they work. Pragmatism can be found in Kant's doctrine of the primary of practical over pure reason, and continued to play an influential role in the theory of meaning and of truth.
In case of fact, the philosophy of mind is the modern successor to behaviourism, as do the functionalism that its early advocates were Putnam (1926- ) and Sellars (1912-89), and its guiding principle is that we can define mental states by a triplet of relations they have on other mental stares, what effects they have on behaviour. The definition need not take the form of a simple analysis, but if w could write down the totality of axioms, or postdate, or platitudes that govern our theories about what things of other mental states, and our theories about what things are apt to cause (for example), a belief state, what effects it would have on a variety of other mental states, and what the force of impression of one thing on another, inducing to come into being and carry to as successful conclusions as found a pass that allowed them to affect passage through the mountains. A condition or occurrence traceable to a cause drawing forth the underlying and hidden layers of deep-seated latencies. Very well protected but the digression belongs to the patient, in that, what exists of the back-burners of the mind, slowly simmering, and very much of your self control is intact: Furthering the outcry of latent incestuousness that affects the likelihood of having an influence upon behaviour, so then all that we would have done otherwise, contains all that is needed to make the state a proper theoretical notion. It could be implicitly defied by these theses. Functionalism is often compared with descriptions of a computer, since according to mental descriptions correspond to a description of a machine in terms of software, that remains silent about the underlying hardware or 'realization' of the program the machine is running. The principal advantage of functionalism includes its fit with the way we know of mental states both of ourselves and others, which is via their effects on behaviour and other mental states. As with behaviourism, critics charge that structurally complex items that do not bear mental states might nevertheless, imitate the functions that are cited. According to this criticism functionalism is too generous and would count too many things as having minds. It is also queried whether functionalism is too paradoxical, able to see mental similarities only when there is causal similarity, when our actual practices of interpretations enable us to support thoughts and desires too differently from our own, it may then seem as though beliefs and desires are obtained in the consenting availability of 'variably acquired' causal architecture, just as much as they can be in different Neurophysiologic states.
The philosophical movement of Pragmatism had a major impact on American culture from the late 19th century to the present. Pragmatism calls for ideas and theories to be tested in practice, by assessing whether acting upon the idea or theory produces desirable or undesirable results. According to pragmatists, all claims about truth, knowledge, morality, and politics must be tested in this way. Pragmatism has been critical of traditional Western philosophy, especially the notions that there are absolute truths and absolute values. Although pragmatism was popular for a time in France, England, and Italy, most observers believe that it encapsulates an American faith in know-how and practicality and an equally American distrust of abstract theories and ideologies.
In mentioning the American psychologist and philosopher we find William James, who helped to popularize the philosophy of pragmatism with his book Pragmatism: A New Name for Old Ways of thinking (1907). Influenced by a theory of meaning and verification developed for scientific hypotheses by American philosopher C.S. Peirce, James held that truth is what compellingly works, or has good experimental results. In a related theory, James argued the existence of God is partly verifiable because many people derive benefits from believing.
Pragmatists regard all theories and institutions as tentative hypotheses and solutions. For this reason they believed that efforts to improve society, through such means as education or politics, must be geared toward problem solving and must be ongoing. Through their emphasis on connecting theory to practice, pragmatist thinkers attempted to transform all areas of philosophy, from metaphysics to ethics and political philosophy.
Pragmatism sought a middle ground between traditional ideas about the nature of reality and radical theories of nihilism and irrationalism, which had become popular in Europe in the late 19th century. Traditional metaphysics assumed that the world has a fixed, intelligible structure and that human beings can know absolute or objective truths about the world and about what constitutes moral behaviour. Nihilism and irrationalism, on the other hand, denied those very assumptions and their certitude. Pragmatists today still try to steer a middle course between contemporary offshoots of these two extremes.
The ideas of the pragmatists were considered revolutionary when they first appeared. To some critics, pragmatism's refusal to affirm any absolutes carried negative implications for society. For example, pragmatists do not believe that a single absolute idea of goodness or justice exists, but rather than these concepts are changeable and depend on the context in which they are being discussed. The absence of these absolutes, critics feared, could result in a decline in moral standards. The pragmatists' denial of absolutes, moreover, challenged the foundations of religion, government, and schools of thought. As a result, pragmatism influenced developments in psychology, sociology, education, semiotics (the study of signs and symbols), and scientific method, as well as philosophy, cultural criticism, and social reform movements. Various political groups have also drawn on the assumptions of pragmatism, from the progressive movements of the early 20th century to later experiments in social reform.
Pragmatism is best understood in its historical and cultural context. It arose during the late 19th century, a period of rapid scientific advancement typified by the theories of British biologist Charles Darwin, whose theories suggested too many thinkers that humanity and society are in a perpetual state of progress. During this same period a decline in traditional religious beliefs and values accompanied the industrialization and material progress of the time. In consequence it became necessary to rethink fundamental ideas about values, religion, science, community, and individuality.
The three most important pragmatists are American philosophers' Charles Sanders Peirce, William James, and John Dewey. Peirce was primarily interested in scientific method and mathematics; His objective was to infuse scientific thinking into philosophy and society and he believed that human comprehension of reality was becoming ever greater and that human communities were becoming increasingly progressive. Peirce developed pragmatism as a theory of meaning - in particular, the meaning of concepts used in science. The meaning of the concept 'brittle', for example, is given by the observed consequences or properties that objects called 'brittle' exhibit. For Peirce, the only rational way to increase knowledge was to form mental habits that would test ideas through observation, experimentation, or what he called inquiry. Many philosophers known as logical positivist, a group of philosophers who have been influenced by Peirce, believed that our evolving species was fated to get ever closer to Truth. Logical positivists emphasize the importance of scientific verification, rejecting the assertion of positivism that personal experience is the basis of true knowledge.
James moved pragmatism in directions that Peirce strongly disliked. He generalized Peirce's doctrines to encompass all concepts, beliefs, and actions; he also applied pragmatist ideas to truth as well as to meaning. James was primarily interested in showing how systems of morality, religion, and faith could be defended in a scientific civilization. He argued that sentiment, as well as logic is crucial to rationality and that the great issues of life - morality and religious belief, for example - are leaps of faith. As such, they depend upon what he called 'the will to believe' and not merely on scientific evidence, which can never tell us what to do or what is worthwhile. Critics charged James with relativism (the belief that values depend on specific situations) and with crass expediency for proposing that if an idea or action works the way one intends, it must be right. But James can more accurately be described as a pluralist - someone who believes the world to be far too complex for any-one philosophy to explain everything.
Dewey's philosophy can be described as a version of philosophical naturalism, which regards human experience, intelligence, and communities as ever-evolving mechanisms. Using their experience and intelligence, Dewey believed, human beings can solve problems, including social problems, through inquiry. For Dewey, naturalism led to the idea of a democratic society that allows all members to acquire social intelligence and progress both as individuals and as communities. Dewey held that traditional ideas about knowledge, truth, and values, in which absolutes are assumed, are incompatible with a broadly Darwinian world-view in which individuals and societies are progressing. In consequence, he felt that these traditional ideas must be discarded or revised. Indeed, for pragmatists, everything people know and do depend on a historical context and are thus tentative rather than absolute.
Many followers and critics of Dewey believe he advocated elitism and social engineering in his philosophical stance. Others think of him as a kind of romantic humanist. Both tendencies are evident in Dewey's writings, although he aspired to synthesize the two realms.
The pragmatists' tradition was revitalized in the 1980s by American philosopher Richard Rorty, who has faced similar charges of elitism for his belief in the relativism of values and his emphasis on the role of the individual in attaining knowledge. Interest has renewed in the classic pragmatists - Pierce, James, and Dewey - have an alternative to Rorty's interpretation of the tradition.
One of the earliest versions of a correspondence theory was put forward in the 4th century Bc Greek philosopher Plato, who sought to understand the meaning of knowledge and how it is acquired. Plato wished to distinguish between true belief and false belief. He proposed a theory based on intuitive recognition that true statements correspond to the facts - that is, agree with reality - while false statements do not. In Plato's example, the sentence "Theaetetus flies" can be true only if the world contains the fact that Theaetetus flies. However, Plato - and much later, 20th-century British philosopher Bertrand Russell - recognized this theory as unsatisfactory because it did not allow for false belief. Both Plato and Russell reasoned that if a belief is false because there is no fact to which it corresponds, it would then be a belief about nothing and so not a belief at all. Each then speculated that the grammar of a sentence could offer a way around this problem. A sentence can be about something (the person Theaetetus), yet false (flying is not true of Theaetetus). But how, they asked, are the parts of a sentence related to reality?
One suggestion, proposed by 20th-century philosopher Ludwig Wittgenstein, is that the parts of a sentence relate to the objects they describe in much the same way that the parts of a picture relate to the objects pictured. Once again, however, false sentences pose a problem: If a false sentence pictures nothing, there can be no meaning in the sentence.
In the late 19th-century American philosopher Charles S. Peirce offered another answer to the question "What is truth?" He asserted that truth is that which experts will agree upon when their investigations are final. Many pragmatists such as Peirce claim that the truth of our ideas must be tested through practice. Some pragmatists have gone so far as to question the usefulness of the idea of truth, arguing that in evaluating our beliefs we should rather pay attention to the consequences that our beliefs may have. However, critics of the pragmatic theory are concerned that we would have no knowledge because we do not know which set of beliefs will ultimately be agreed upon; nor are their sets of beliefs that are useful in every context.
A third theory of truth, the coherence theory, also concerns the meaning of knowledge. Coherence theorists have claimed that a set of beliefs is true if the beliefs are comprehensive - that is, they cover everything - and do not contradict each other.
Other philosophers dismiss the question "What is truth?" With the observation that attaching the claim 'it is true that' to a sentence adds no meaning, however, these theorists, who have proposed what are known as deflationary theories of truth, do not dismiss such talk about truth as useless. They agree that there are contexts in which a sentence such as 'it is true that the book is blue' can have a different impact than the shorter statement 'the book is blue'. What is more important, use of the word true is essential when making a general claim about everything, nothing, or something, as in the statement 'most of what he says is true?'
Many experts believe that philosophy as an intellectual discipline originated with the work of Plato, one of the most celebrated philosophers in history. The Greek thinker had an immeasurable influence on Western thought. However, Plato's expression of ideas in the form of dialogues-the dialectical method, used most famously by his teacher Socrates - has led to difficulties in interpreting some of the finer points of his thoughts. The issue of what exactly Plato meant to say is addressed in the following excerpt by author R. M. Hare.
Linguistic analysis as a method of philosophy is as old as the Greeks. Several of the dialogues of Plato, for example, are specifically concerned with clarifying terms and concepts. Nevertheless, this style of philosophizing has received dramatically renewed emphasis in the 20th century. Influenced by the earlier British empirical tradition of John Locke, George Berkeley, David Hume, and John Stuart Mill and by the writings of the German mathematician and philosopher Gottlob Frége, the 20th-century English philosopher's G. E. Moore and Bertrand Russell became the founders of this contemporary analytic and linguistic trend. As students together at the University of Cambridge, Moore and Russell rejected Hegelian idealism, particularly as it was reflected in the work of the English metaphysician F. H. Bradley, who held that nothing is completely real except the Absolute. In their opposition to idealism and in their commitment to the view that careful attention to language is crucial in philosophical inquiry, and they set the mood and style of philosophizing for much of the 20th century English-speaking world.
For Moore, philosophy was first and foremost analysis. The philosophical task involves clarifying puzzling propositions or concepts by indicating fewer puzzling propositions or concepts to which the originals are held to be logically equivalent. Once this task has been completed, the truth or falsity of problematic philosophical assertions can be determined more adequately. Moore was noted for his careful analyses of such puzzling philosophical claims as 'time is unreal', analyses that aided of determining the truth of such assertions.
Russell, strongly influenced by the precision of mathematics, was concerned with developing an ideal logical language that would accurately reflect the nature of the world. Complex propositions, Russell maintained, can be resolved into their simplest components, which he called atomic propositions. These propositions refer to atomic facts, the ultimate constituents of the universe. The metaphysical view based on this logical analysis of language and the insistence that meaningful propositions must correspond to facts constitutes what Russell called logical atomism. His interest in the structure of language also led him to distinguish between the grammatical form of a proposition and its logical form. The statements 'John is good' and 'John is tall' have the same grammatical form but different logical forms. Failure to recognize this would lead one to treat the property 'goodness' as if it were a characteristic of John in the same way that the property 'tallness' is a characteristic of John. Such failure results in philosophical confusion.
Austrian-born philosopher Ludwig Wittgenstein was one of the most influential thinkers of the 20th century. With his fundamental work, Tractatus Logico-philosophicus, published in 1921, he became a central figure in the movement known as analytic and linguistic philosophy.
Russell's work of mathematics attracted towards studying in Cambridge the Austrian philosopher Ludwig Wittgenstein, who became a central figure in the analytic and linguistic movement. In his first major work, Tractatus Logico-Philosophicus (1921; translation 1922), in which he first presented his theory of language, Wittgenstein argued that 'all philosophy is a 'critique of language' and that 'philosophy aims at the logical clarification of thoughts'. The results of Wittgenstein's analysis resembled Russell's logical atomism. The world, he argued, is ultimately composed of simple facts, which it is the purpose of language to picture. To be meaningful, statements about the world must be reducible to linguistic utterances that have a structure similar to the simple facts pictured. In this early Wittgensteinian analysis, only propositions that picture facts - the propositions of science - are considered factually meaningful. Metaphysical, theological, and ethical sentences were judged to be factually meaningless.
Influenced by Russell, Wittgenstein, Ernst Mach, and others, a group of philosophers and mathematicians in Vienna in the 1920s initiated the movement known as logical positivism: Led by Moritz Schlick and Rudolf Carnap, the Vienna Circle initiated one of the most important chapters in the history of analytic and linguistic philosophy. According to the positivists, the task of philosophy is the clarification of meaning, not the discovery of new facts (the job of the scientists) or the construction of comprehensive accounts of reality (the misguided pursuit of traditional metaphysics).
The positivists divided all meaningful assertions into two classes: analytic propositions and empirically verifiable ones. Analytic propositions, which include the propositions of logic and mathematics, are statements the truth or falsity of which depend altogether on the meanings of the terms constituting the statement. An example would be the proposition 'two plus two equals four'. The second class of meaningful propositions includes all statements about the world that can be verified, at least in principle, by sense experience. Indeed, the meaning of such propositions is identified with the empirical method of their verification. This verifiability theory of meaning, the positivists concluded, would demonstrate that scientific statements are legitimate factual claims and that metaphysical, religious, and ethical sentences are factually dwindling. The ideas of logical positivism were made popular in England by the publication of A. J. Ayer's Language, Truth and Logic in 1936.
The positivists' verifiability theory of meaning came under intense criticism by philosophers such as the Austrian-born British philosopher Karl Popper. Eventually this narrow theory of meaning yielded to a broader understanding of the nature of language. Again, an influential figure was Wittgenstein. Repudiating many of his earlier conclusions in the Tractatus, he initiated a new line of thought culminating in his posthumously published Philosophical Investigations (1953, translated 1953). In this work, Wittgenstein argued that once attention is directed to the way language is actually used in ordinary discourse, the variety and flexibility of language become clear. Propositions do much more than simply picture facts.
This recognition led to Wittgenstein's influential concept of language games. The scientist, the poet, and the theologian, for example, are involved in different language games. Moreover, the meaning of a proposition must be understood in its context, that is, in terms of the rules of the language game of which that proposition is a part. Philosophy, concluded Wittgenstein, is an attempt to resolve problems that arise as the result of linguistic confusion, and the key to the resolution of such problems is ordinary language analysis and the proper use of language.
Additional contributions within the analytic and linguistic movement include the work of the British philosopher's Gilbert Ryle, John Austin, and P. F. Strawson and the American philosopher W. V. Quine. According to Ryle, the task of philosophy is to restate 'systematically misleading expressions' in forms that are logically more accurate. He was particularly concerned with statements the grammatical form of which suggests the existence of nonexistent objects. For example, Ryle is best known for his analysis of communicably communicated linguistic languages, language that has its roots as grounded in a Mentalistic and misleadingly suggests that the mind is one that has real and independent existence where each entity of the series requires separate study, and in the same way as the body.
Austin maintained that one of the most fruitful starting points for philosophical inquiry is attention to the extremely fine distinctions drawn in ordinary language. His analysis of language eventually led to a general theory of speech acts, that is, to a description of the variety of activities that an individual may be performing when something is uttered.
Strawson is known for his analysis of the relationship between formal logic and ordinary language. The complexity of the latter, he argued, is inadequately represented by formal logic. A variety of analytic tools, therefore, are needed in addition to logic in analysing ordinary language.
Quine discussed the relationship between language and ontology. He argued that language systems tend to commit their users to the existence of certain things. For Quine, the justification for speaking one way rather than another is a thoroughly pragmatic one.
The commitment to language analysis as a way of pursuing philosophy has continued as a significant contemporary dimension in philosophy. A division also continues to exist between those who prefer to work with the precision and rigour of symbolic logical systems and those who prefer to analyse ordinary language. Although few contemporary philosophers maintain that all philosophical problems are linguistic, the view continues to be widely held that attention to the logical structure of language and to how language is used in everyday discourse can many a time have an eye to aid in anatomize Philosophical problems.
A loose title for various philosophies that emphasize certain common themes, the individual, the experience of choice, and the absence of rational understanding of the universe, with the additional ways of addition seems a consternation of dismay or one fear, or the other extreme, as far apart is the sense of the dottiness of 'absurdity in human life', however, existentialism is a philosophical movement or tendency, emphasizing individual existence, freedom, and choice, that influenced many diverse writers in the 19th and 20th centuries.
Because of the diversity of positions associated with existentialism, the term is impossible to define precisely. Certain themes common to virtually all existentialist writers can, however, be identified. The term itself suggests one major theme: the stress on concrete individual existence and, consequently, on subjectivity, individual freedom, and choice.
Most philosophers since Plato have held that the highest ethical good are the same for everyone; Insofar as one approaches moral perfection, one resembles other morally perfect individuals. The 19th-century Danish philosopher Søren Kierkegaard, who was the first writer to call himself existential, reacted against this tradition by insisting that the highest good for the individual are to find his or her own unique vocation. As he wrote in his journal, 'I must find a truth that is true for me . . . the idea for which I can live or die'. Other existentialist writers have echoed Kierkegaard's belief that one must choose one's own way without the aid of universal, objective standards. Against the traditional view that moral choice involves an objective judgment of right and wrong, existentialists have argued that no objective, rational basis can be found for moral decisions. The 19th-century German philosopher Friedrich Nietzsche further contended that the individual must decide which situations are to count as moral situations.
Nevertheless, renowned as one of the most important writers in world history, 19th-century Russian author Fyodor Dostoyevsky wrote psychologically intense novels which probed the motivations and moral justifications for his characters' actions. Dostoyevsky commonly addressed themes such as the struggle between good and evil within the human soul and the idea of salvation through suffering. The Brothers Karamazov (1879-1880), generally considered Dostoyevsky's best work, interlaces religious exploration with the story of a family's violent quarrels over a woman and a disputed inheritance.
A number of existentialist philosophers used literary forms to convey their thought, and existentialism has been as vital and as extensive a movement in literature as in philosophy. The 19th-century Russian novelist Fyodor Dostoyevsky is probably the greatest existentialist literary figure. In Notes from the Underground (1864), the alienated antihero rages against the optimistic assumptions of rationalist humanism. The view of human nature that emerges in this and other novels of Dostoyevsky is that it is unpredictable and perversely self-destructive; only Christian love can save humanity from itself, but such love cannot be understood philosophically. As the character Alyosha says in The Brothers Karamazov (1879-80), "We must love life more than the meaning of it."
The opening series of arranged passages in continuous or uniform order, by ways that the progressive course accommodates to arrange in a line or lines of continuity, Wherefore, the Russian novelist Fyodor Dostoyevsky's Notes from Underground (1864) - 'I am a sick man . . . I am a spiteful man' - are among the most famous in 19th-century literature. Published five years after his release from prison and involuntary, military service in Siberia, Notes from Underground is a sign of Dostoyevsky's rejection of the radical social thinking he had embraced in his youth. The unnamed narrator is antagonistic in tone, questioning the reader's sense of morality as well as the foundations of rational thinking. In this excerpt from the beginning of the novel, the narrator describes himself, derisively referring to himself as an 'overly conscious' intellectual.
In the 20th century, the novels of the Austrian Jewish writer Franz Kafka, such as The Trial (1925 translations, 1937) and The Castle (1926 translations, 1930), presents isolated men confronting vast, elusive, menacing bureaucracies; Kafka's themes of anxiety, guilt, and solitude reflect the influence of Kierkegaard, Dostoyevsky, and Nietzsche. The influence of Nietzsche is also discernible in the novels of the French writer's André Malraux and in the plays of Sartre. The work of the French writer Albert Camus is usually associated with existentialism because of the prominence in it of such themes as the apparent absurdity and futility of life, the indifference of the universe, and the necessity of engagement in a just cause. In the United States, the influence of existentialism on literature has been more indirect and diffuse, but traces of Kierkegaard's thought can be found in the novels of Walker Percy and John Updike, and various existentialist themes are apparent in the work of such diverse writers as Norman Mailer and John Barth.
The problem of defining knowledge in terms of true belief plus some favoured relation between the believer and the facts began with Plato's view in the Theaetetus, that knowledge is true belief plus some logos, and epistemology is a beginning for which it is bound to the foundations of knowledge, a special branch of philosophy that addresses the philosophical problems surrounding the theory of knowledge. Epistemology is concerned with the definition of knowledge and related concepts, the sources and criteria of knowledge, the kinds of knowledge possible and the degree to which each is certain, and the exact integrations among the one's who are understandably of knowing and the object known.
Thirteenth-century Italian philosopher and theologian Saint Thomas Aquinas attempted to synthesize Christian belief with a broad range of human knowledge, embracing diverse sources such as Greek philosopher Aristotle and Islamic and Jewish scholars. His thought exerted lasting influence on the development of Christian theology and Western philosophy. And explicated by the author, Anthony Kenny who examines the complexities of Aquinas's concepts of substance and accident.
In the 5th century Bc, the Greek Sophists questioned the possibility of reliable and objective knowledge. Thus, a leading Sophist, Gorgias, argued that nothing really exists, that if anything did exist it could not be known, and that if knowledge were possible, it could not be communicated. Another prominent Sophist, Protagoras, maintained that no person's opinions can be said to be more correct than another's, because each is the sole judge of his or her own experience. Plato, following his illustrious teacher Socrates, tried to answer the Sophists by postulating the existence of a world of unchanging and invisible forms, or ideas, about which it is possible to have exact and certain knowledge. The thing's one sees and touches, they maintained, are imperfect copies of the pure forms studied in mathematics and philosophy. Accordingly, only the abstract reasoning of these disciplines yields genuine knowledge, whereas reliance on sense perception produces vague and inconsistent opinions. They concluded that philosophical contemplation of the unseen world of forms is the highest goal of human life.
Aristotle followed Plato in regarding abstract knowledge as superior to any other, but disagreed with him as to the proper method of achieving it. Aristotle maintained that almost all knowledge is derived from experience. Knowledge is gained either directly, by abstracting the defining traits of a species, or indirectly, by deducing new facts from those already known, in accordance with the rules of logic. Careful observation and strict adherence to the rules of logic, which were first set down in systematic form by Aristotle, would help guard against the pitfalls the Sophists had exposed. The Stoic and Epicurean schools agreed with Aristotle that knowledge originates in sense perception, but against both Aristotle and Plato they maintained that philosophy is to be valued as a practical guide to life, rather than as an end in itself.
After many centuries of declining interest in rational and scientific knowledge, the Scholastic philosopher Saint Thomas Aquinas and other philosophers of the middle Ages helped to restore confidence in reason and experience, blending rational methods with faith into a unified system of beliefs. Aquinas followed Aristotle in regarding perception as the starting point and logic as the intellectual procedure for arriving at reliable knowledge of nature, but he considered faith in scriptural authority as the main source of religious belief.
From the 17th to the late 19th century, the main issue in epistemology was reasoning versus sense perception in acquiring knowledge. For the rationalists, of whom the French philosopher René Descartes, the Dutch philosopher Baruch Spinoza, and the German philosopher Gottfried Wilhelm Leibniz were the leaders, the main source and final test of knowledge was deductive reasoning based on self-evident principles, or axioms. For the empiricists, beginning with the English philosophers Francis Bacon and John Locke, the main source and final test of knowledge was sense perception.
Bacon inaugurated the new era of modern science by criticizing the medieval reliance on tradition and authority and also by setting down new rules of scientific method, including the first set of rules of inductive logic ever formulated. Locke attacked the rationalist belief that the principles of knowledge are intuitively self-evident, arguing that all knowledge is derived from experience, either from experience of the external world, which stamps sensations on the mind, or from internal experience, in which the mind reflects on its own activities. Human knowledge of external physical objects, he claimed, is always subject to the errors of the senses, and he concluded that one cannot have absolutely certain knowledge of the physical world.
Irish-born philosopher and clergyman George Berkeley (1685-1753) argued that of everything a human being conceived of exists, as an idea in a mind, a philosophical focus which is known as idealism. Berkeley reasoned that because one cannot control one's thoughts, they must come directly from a larger mind: that of God. In this excerpt from his Treatise Concerning the Principles of Human Knowledge, written in 1710, Berkeley explained why he believed that it is 'impossible . . . that there should be any such thing as an outward object'.
The Irish philosopher George Berkeley acknowledged along with Locke, that knowledge occurs through ideas, but he denied Locke's belief that a distinction can appear between ideas and objects. The British philosopher David Hume continued the empiricist tradition, but he did not accept Berkeley's conclusion that knowledge was of ideas only. He divided all knowledge into two kinds: Knowledge of relations of ideas - that is, the knowledge found in mathematics and logic, which is exact and certain but provide no information about the world. Knowledge of matters of fact - that is, the knowledge derived from sense perception. Hume argued that most knowledge of matters of fact depends upon cause and effect, and since no logical connection exists between any given cause and its effect, one cannot hope to know any future matter of fact with certainty. Thus, the most reliable laws of science might not remain true - a conclusion that had a revolutionary impact on philosophy.
The German philosopher Immanuel Kant tried to solve the crisis precipitated by Locke and brought to a climax by Hume; His proposed solution combined elements of rationalism with elements of empiricism. He agreed with the rationalists, one can have exact and certain knowledge, but he followed the empiricists in holding that such knowledge is more informative. Adding upon a proposed structure of thought than about the world outside of thought, and distinguishing upon three kinds of knowledge: Analytical deduction, which is exact and certain but uninformative, because it makes clear only what is contained in definitions; synthetic a posterior, which conveys information about the world learned from experience, but is subject to the errors of the senses; and synthetic a priori, which is discovered by pure intuition and is both exact and certain, for it expresses the necessary conditions that the mind imposes on all objects of experience. Mathematics and philosophy, according to Kant, provide this last. Since the time of Kant, one of the most frequently argued questions in philosophy has been whether or not such a thing as synthetic a priori knowledge really exists.
During the 19th century, the German philosopher Georg Wilhelm Friedrich Hegel revived the rationalist claim that absolutely certain knowledge of reality can be obtained by equating the processes of thought, of nature, and of history. Hegel inspired an interest in history and a historical approach to knowledge that was further emphasized by Herbert Spencer in Britain and by the German school of historicisms. Spencer and the French philosopher Auguste Comte brought attention to the importance of sociology as a branch of knowledge and both extended the principles of empiricism to the study of society.
The American school of pragmatism, founded by the philosophers Charles Sanders Peirce, William James, and John Dewey at the turn of this century, carried empiricism further by maintaining that knowledge is an instrument of action and that all beliefs should be judged by their usefulness as rules for predicting experiences.
In the early 20th century, epistemological problems were discussed thoroughly, and subtle shades of difference grew into rival schools of thought. Special attention was given to the relation between the act of perceiving something, the object directly perceived, and the thing that can be said to be known as a result of the perception. The phenomenon’s lists contended that the objects of knowledge are the same as the objects perceived. The neutralists argued that one has direct perceptions of physical objects or parts of physical objects, rather than of one's own mental states. The critical realists took a middle position, holding that although one perceives only sensory data such as colours and sounds, these stand for physical objects and provide knowledge thereof.
A method for dealing with the problem of clarifying the relation between the act of knowing and the object known was developed by the German philosopher Edmund Husserl. He outlined an elaborate procedure that he called phenomenology, by which one is said to be able to distinguish the way things appear to be from the way one thinks they really are, thus gaining a more precise understanding of the conceptual foundations of knowledge.
During the second quarter of the 20th century, two schools of thought emerged, each indebted to the Austrian philosopher Ludwig Wittgenstein. The first of these schools, logical empiricism, or logical positivism, had its origins in Vienna, Austria, but it soon spread to England and the United States. The logical empiricists insisted that there is only one kind of knowledge: scientific knowledge; that any valid knowledge claim must be verifiable in experience; and hence that much that had passed for philosophy was neither true nor false but literally meaningless. Finally, following Hume and Kant, a clear distinction must be maintained between analytic and synthetic statements. The so-called verifiability criterion of meaning has undergone changes as a result of discussions among the logical empiricists themselves, as well as their critics, but has not been discarded. More recently, the sharp distinction between the analytic and the synthetic has been attacked by a number of philosophers, chiefly by American philosopher W.V.O. Quine, whose overall approach is in the pragmatic tradition.
The latter of these recent schools of thought, generally referred to as linguistic analysis, or ordinary language philosophy, seem to break with traditional epistemology. The linguistic analysts undertake to examine the actual way key epistemological terms are used - terms such as knowledge, perception, and probability - and to formulate definitive rules for their use in order to avoid verbal confusion. British philosopher John Langshaw Austin argued, for example, that to say a statement was true, and add nothing to the statement except a promise by the speaker or writer. Austin does not consider truth a quality or property attaching to statements or utterances. However, the ruling thought is that it is only through a correct appreciation of the role and point of this language is that we can come to a better conceptual understanding of what the language is about, and avoid the oversimplifications and distortion we are apt to bring to its subject matter.
Linguistics is the scientific study of language. It encompasses the description of languages, the study of their origin, and the analysis of how children acquire language and how people learn languages other than their own. Linguistics is also concerned with relationships between languages and with the ways languages change over time. Linguists may study language as a thought process and seek a theory that accounts for the universal human capacity to produce and understand language. Some linguists examine language within a cultural context. By observing talk, they try to determine what a person needs to know in order to speak appropriately in different settings, such as the workplace, among friends, or among family. Other linguists focus on what happens when speakers from different language and cultural backgrounds interact. Linguists may also concentrate on how to help people learn another language, using what they know about the learner's first language and about the language being acquired.
Although there are many ways of studying language, most approaches belong to one of the two main branches of linguistics: descriptive linguistics and comparative linguistics.
Descriptive linguistics is the study and analysis of spoken language. The techniques of descriptive linguistics were devised by German American anthropologist Franz Boas and American linguist and anthropologist Edward Sapir in the early 1900s to record and analyse Native American languages. Descriptive linguistics begins with what a linguist hears native speakers say. By listening to native speakers, the linguist gathered a body of data and analyses' it in order to identify distinctive sounds, called phonemes. Individual phonemes, such as /p/ and /b/, are established on the grounds that substitution of one for the other changes the meaning of a word. After identifying the entire inventory of sounds in a language, the linguist looks at how these sounds combine to create morphemes, or units of sound that carry meaning, such as the words push and bush. Morphemes may be individual words such as push; root words, such as the berry in a blueberry; or prefixes (pre- in preview) and suffixes (-ness in openness).
The linguist's next step is to see how morphemes combine into sentences, obeying both the dictionary meaning of the morpheme and the grammatical rules of the sentence. In the sentence "She pushed the bush," the morpheme she, a pronoun, is the subject 'push', a transitive verb, is the verb 'the', a definite article, is the determiner, and bush, a noun, is the object. Knowing the function of the morphemes in the sentence enables the linguist to describe the grammar of the language. The scientific procedures of phonemics (finding phonemes), morphology (discovering morphemes), and syntax (describing the order of morphemes and their function) provides descriptive linguists with a way to write down grammars of languages never before written down or analysed. In this way they can begin to study and understand these languages.
Comparative linguistics is the study and analysis, by means of written records, of the origins and relatedness of different languages. In 1786 Sir William Jones, a British scholar, asserted that Sanskrit, Greek, and Latins were related to each other and had descended from a common source. He based this assertion on observations of similarities in sounds and meanings among the three languages. For example, the Sanskrit word borate for "brother" resembles the Latin word frater, the Greek word phrater, (and the English word brother).
Other scholars went on to compare Icelandic with Scandinavian languages, and Germanic languages with Sanskrit, Greek, and Latin. The correspondences among languages, known as genetic relationships, came to be represented on what comparative linguists refer to as family trees. Family trees established by comparative linguists include the Indo-European, relating Sanskrit, Greek, Latin, German, English, and other Asian and European languages; the Algonquian, relating Fox, Cree, Menomini, Ojibwa, and other Native North American languages; and the Bantu, relating Swahili, Xhosa, Zulu, Kikuyu, and other African languages.
Comparative linguists also look for similarities in the way words are formed in different languages. Latin and English, for example, change the form of a word to express different meanings, as when the English verbs 'go', changes too, 'went' and 'gone' to express a past action. Chinese, on the other hand, has no such inflected forms; the verb remains the same while other words indicate the time (as in "go store tomorrow"). In Swahili, prefixes, suffixes, and infixes (additions in the body of the word) combine with a root word to change its meaning. For example, a single word might be express when something was done, by whom, to whom, and in what manner.
Some comparative linguists reconstruct hypothetical ancestral languages known as proto-languages, which they use to demonstrate relatedness among contemporary languages. A proto-language is not intended to depict a real language, however, and does not represent the speech of ancestors of people speaking modern languages. Unfortunately, some groups have mistakenly used such reconstructions in efforts to demonstrate the ancestral homeland of people.
Comparative linguists have suggested that certain basic words in a language do not change over time, because people are reluctant to introduce new words for such constants as arm, eye, or mother. These words are termed culture free. By comparing lists of culture-free words in languages within a family, linguists can derive the percentage of related words and use a formula to figure out when the languages separated from one another.
By the 1960s comparativists were no longer satisfied with focussing on origins, migrations, and the family tree method. They challenged as unrealistic the notion that an earlier language could remain sufficiently isolated for other languages to be derived exclusively from it over a period of time. Today comparativists seek to understand the more complicated reality of language history, taking language contact into account. They are concerned with universal characteristics of language and with comparisons of grammars and structures.
The field of linguistics, which lends from its own theories and methods into other disciplines, and many subfields of linguistics have expanded our understanding of languages. Linguistic theories and methods are also used in other fields of study. These overlapping interests have led to the creation of several cross-disciplinary fields.
Sociolinguistic study of patterns and variations in language within a society or community. It focuses on the way people use language to express social class, group status, gender, or ethnicity, and it looks at how they make choices about the form of language they use. It also examines the way people use language to negotiate their role in society and to achieve positions of power. For example, sociolinguistic studies have found that the way a New Yorker pronounces the phoneme /r/ in an expression such as "fourth floor" can indicate the person's social class. According to one study, people aspiring to move from the lower middle class to the upper middle class attach prestige to pronouncing /r/. Sometimes they even overcorrect their speech, pronouncing /r/ where those whom they wish to copy may not.
Some Sociolinguists believe that analysing such variables as the use of a particular phoneme can predict the direction of language change. Change, they say, moves toward the variable associated with power, prestige, or other quality having high social value. Other Sociolinguists focus on what happens when speakers of different languages interact. This approach to language change emphasizes the way languages mix rather than the direction of change within a community. The goal of a Sociolinguistical understanding, perhaps, takes a position whereby a communicative competence - what people need to know to use the appropriate language for a given social setting.
Psycholinguistics merge the fields of psychology and linguistics to study how people process language and how language use is related to underlying mental processes. Studies of children's language acquisition and of second-language acquisition are psycholinguistic in nature. Psycholinguists work to develop models for how language is processed and understood, using evidence from studies of what happens when these processes go awry. They also study language disorders such as aphasia (impairment of the ability to use or comprehend words) and dyslexia (impairment of the ability to make out written language).
Computational linguistics involves the use of computers to compile linguistic data, analyse languages, translate from one language to another, and develop and test models of language processing. Linguists use computers and large samples of actual language to analyse the relatedness and the structure of languages and to look for patterns and similarities. Computers also assist in stylistic studies, information retrieval, various forms of textual analysis, and the construction of dictionaries and concordances. Applying computers to language studies has resulted in a machine translated systems and machines that recognize and produce speech and text. Such machines facilitate communication with humans, including those who are perceptually or linguistically impaired.
Applied linguistics employs linguistic theory and methods in teaching and in research on learning a second language. Linguists look at the errors people make as they learn another language and at their strategies for communicating in the new language at different degrees of competence. In seeking to understand what happens in the mind of the learner, applied linguists recognize that motivation, attitude, learning style, and personality affect how well a person learns another language.
Anthropological linguistics, also known as linguistic anthropology, uses linguistic approaches to analyse culture. Anthropological linguists examine the relationship between a culture and its language. The way cultures and languages have moderately changed uninterruptedly through intermittent intervals of time. And how various cultures and languages are related to each other, for example, the present English usage of family and given names arose in the late 13th and early 14th centuries when the laws concerning registration, tenure, and inheritance of property were changed.
Once linguists began to study language as a set of abstract rules that somehow account for speech, other scholars began to take an interest in the field. They drew analogies between language and other forms of human behaviour, based on the belief that a shared structure underlies many aspects of a culture. Anthropologists, for example, became interested in a structuralist approach to the interpretation of kinship systems and analysis of myth and religion. American linguist Leonard Bloomfield promoted structuralism in the United States.
Saussure's ideas also influenced European linguistics, most notably in France and Czechoslovakia (now the Czech Republic). In 1926 Czech linguist Vilem Mathesius founded the Linguistic Circle of Prague, a group that expanded the focus of the field to include the context of language use. The Prague circle developed the field of phonology, or the study of sounds, and demonstrated that universal features of sounds in the languages of the world interrelate in a systematic way. Linguistic analysis, they said, should focus on the distinctiveness of sounds rather than on the ways they combine. Where descriptivist tried to locate and describe individual phonemes, such as /b/ and /p/, the Prague linguists stressed the features of these phonemes and their interrelationships in different languages. In English, for example, the voice distinguishes between the similar sounds of /b/ and /p/, but these are not distinct phonemes in a number of other languages. An Arabic speaker might pronounce the cities Pompeii and Bombay the same way.
As linguistics developed in the 20th century, the notion became prevalent that language is more than speech - specifically, that it is an abstract system of interrelationships shared by members of a speech community. Structural linguistics led linguists to look at the rules and the patterns of behaviour shared by such communities. Whereas structural linguists saw the basis of language in the social structure, other linguists looked at language as a mental process.
The 1957 publication of ”Syntactic Structures” by American linguist Noam Chomsky initiated what many views as a scientific revolution in linguistics. Chomsky sought a theory that would account for both linguistic structure and the creativity of language - the fact that we can create entirely original sentences and understand sentences never before uttered. He proposed that all people have an innate ability to acquire language. The task of the linguist, he claimed, is to describe this universal human ability, known as language competence, with a grammar from which the grammars of all languages could be derived. The linguist would develop this grammar by looking at the rules children use in hearing and speaking their first language. He termed the resulting model, or grammar, a transformational-generative grammar, referring to the transformations (or rules) that create (or account for) language. Certain rules, Chomsky asserted, are shared by all languages and form part of a universal grammar, while others are language specific and associated with particular speech communities. Since the 1960s much of the development in the field of linguistics has been a reaction to or against Chomsky's theories.
At the end of the 20th century, linguists used the term grammar primarily to refer to a subconscious linguistic system that enables people to produce and comprehend an unlimited number of utterances. Grammar thus accounts for our linguistic competence. Observations about the actual language we use, or language performance, are used to theorize about this invisible mechanism known as grammar.
The scientific study of language led by Chomsky has had an impact on nongenerative linguists as well. Comparative and historically oriented linguists are looking for the various ways linguistic universals show up in individual languages. Psycholinguists, interested in language acquisition, are investigating the notion that an ideal speaker-hearer is the origin of the acquisition process. Sociolinguists are examining the rules that underlie the choice of language variants, or codes, and allow for switching from one code to another. Some linguists are studying language performance - the way people use language - to see how it reveals a cognitive ability shared by all human beings. Others seek to understand animal communication within such a framework. What mental processes enable chimpanzees to make signs and communicate with one another and how do these processes differ from those of humans?
From these initial concerns came some of the great themes of twentieth-century philosophy. How exactly does language relate to thought? Are the irredeemable problems about putative private thought? These issues are captured under the general label ‘Lingual Turn’. The subsequent development of those early twentieth-century positions has led to a bewildering heterogeneity in philosophy in the early twenty-first century. the very nature of philosophy is itself radically disputed: Analytic, continental, postmodern, critical theory, feminist t, and non-Western, are all prefixes that give a different meaning when joined to ‘philosophy’. The variety of thriving different schools, the number of professional philosophers, the proliferation of publications, the development of technology in helping research as all manifest a radically different situation to that of one hundred years ago.
As with justification and knowledge, the traditional view of content has been strongly internalist by character. The main argument for externalism derives from the philosophy of language, more specifically from the various phenomena pertaining to natural kind terms, indexicals, etc. that motivate the views that have come to be known as 'direct reference' theories. Such phenomena seem at least to show that the belief or thought content that can be properly attributed to a person is dependant on facts about his environment, e.g., whether he is on Earth or Twin Earth, what is fact pointing at, the classificatory criterion employed by expects in his social group, etc. - not just on what is going on internally in his mind or brain.
An objection to externalist account of content is that they seem unable to do justice to our ability to know the content of our beliefs or thought 'from the inside', simply by reflection. If content is depending on external factors pertaining to the environment, then knowledge of content should depend on knowledge of these factors - which will not in general be available to the person whose belief or thought is in question.
The adoption of an externalist account of mental content would seem to support an externalist account of justification, apart from all contentual beliefs that are unaccessible to the believer, then both the justifying statuses of other beliefs in relation to that of the same representation are the status of that content, being totally rationalized by further beliefs for which it will be similarly unaccessible? Thus, contravening the internalist requirement for justification, as an internalist must insist that there are no justification relations of these sorts, that our internally associable content can also not be warranted or as stated or indicated without the deviated departure from a course or procedure or from a norm or standard in showing no deviation from traditionally held methods of justification exacting by anything else: But such a response appears lame unless it is coupled with an attempt to show that the externalised account of content is mistaken.
Except for alleged cases of thing s that are evident for one just by being true, it has often been thought, anything is known must satisfy certain criteria as well as being true. Except for alleged cases of self-evident truths, it is often thought that anything that is known must satisfy certain criteria or standards. These criteria are general principles that will make a proposition evident or just make accepting it warranted to some degree. Common suggestions for this role include position ‘p’, e.g., that 2 + 2 = 4, ‘p’ is evident or, if ‘p’ coheres wit h the bulk of one’s beliefs, ‘p’ is warranted. These might be criteria whereby putative self-evident truths, e.g., that one clearly and distinctly conceive s ‘p’, ‘transmit’ the status as evident they already have without criteria to other proposition s like ‘p’, or they might be criteria whereby purely non-epistemic considerations, e.g., facts about logical connections or about conception that need not be already evident or warranted, originally ‘create’ p’s epistemic status. If that in turn can be ‘transmitted’ to other propositions, e.g., by deduction or induction, there will be criteria specifying when it is.
Nonetheless, of or relating to tradition a being previously characterized or specified to convey an idea indirectly, as an idea or theory for consideration and being so extreme a design or quality and lean towards an ecocatorial suggestion that implicate an involving responsibility that include: (1) if a proposition ‘p’, e.g., that 2 + 2 = 4, is clearly and distinctly conceived, then ‘p’ is evident, or simply, (2) if we can’t conceive ‘p’ to be false, then ‘p’ is evident: Or, (3) whenever are immediately conscious o f in thought or experience, e.g., that we seem to see red, is evident. These might be criteria whereby putative self-evident truth s, e.g., that one clearly and distinctly conceive, e.g., that one clearly and distinctly conceive ‘p’, ‘transmit’ the status as evident they already have for one without criteria to other propositions like ‘p’. Alternatively, they might be criteria whereby epistemic status, e.g., p’s being evident, is originally created by purely non-epistemic considerations, e.g., facts about how ‘p’ is conceived which are neither self-evident is already criterial evident.
The result effect, holds that traditional criteria do not seem to make evident propositions about anything beyond our own thoughts, experiences and necessary truths, to which deductive or inductive criteria ma y be applied. Moreover, arguably, inductive criteria, including criteria warranting the best explanation of data, never make things evident or warrant their acceptance enough to count as knowledge.
Contemporary epistemologists suggest that traditional criteria may need alteration in three ways. Additional evidence may subject even our most basic judgements to rational correction, though they count as evident on the basis of our criteria. Warrant may be transmitted other than through deductive and inductive relations between propositions. Transmission criteria might not simply ‘pass’ evidence on linearly from a foundation of highly evident ‘premisses’ to ‘conclusions’ that are never more evident.
As with justification and knowledge, the traditional view of content has been strongly internalist in character. The main argument for externalism derives from the philosophy y of language, more specifically from the various phenomena pertaining to natural kind terms, indexicals, etc. that motivate the views that have come to be known as 'direct reference' theories. Such phenomena seem at least to show that the belief or thought content that can be properly attributed to a person is dependant on facts about his environment, e.g., whether he is on Earth or Twin Earth, what is fact pointing at, the classificatory criterion employed by expects in his social group, etc. - not just on what is going on internally in his mind or brain.
Nonetheless, of or relating to tradition a being previously characterized or specified to convey an idea indirectly, as an idea or theory for consideration and being so extreme a design or quality and lean towards an ecocatorial suggestion that implicate an involving responsibilities that include: (1) if a proposition ‘p’, e.g., that 2 + 2 = 4, is clearly and distinctly conceived, then ‘p’ is evident, or simply, (2) if we can’t conceive ‘p’ to be false, then ‘p’ is evident: Or, (3) whenever are immediately conscious o f in thought or experience, e.g., that we seem to see red, is evident. These might be criteria whereby putative self-evident truth s, e.g., that one clearly and distinctly conceive, e.g., that one clearly and distinctly conceive ‘p’, ‘transmit’ the status as evident they already have for one without criteria to other propositions like ‘p’. Alternatively, they might be criteria whereby epistemic status, e.g., p’s being evident, is originally created by purely non-epistemic considerations, e.g., facts about how ‘p’ is conceived which are neither self-evident is already criterial evident.
The result effect, holds that traditional criteria do not seem to make evident propositions about anything beyond our own thoughts, experiences and necessary truths, to which deductive or inductive criteria ma y be applied. Moreover, arguably, inductive criteria, including criteria warranting the best explanation of data, never make things evident or warrant their acceptance enough to count as knowledge.
Contemporary epistemologists suggest that traditional criteria may need alteration in three ways. Additional evidence may subject even our most basic judgements to rational correction, though they count as evident on the basis of our criteria. Warrant may be transmitted other than through deductive and inductive relations between propositions. Transmission criteria might not simply ‘pass’ evidence on linearly from a foundation of highly evident ‘premisses’ to ‘conclusions’ that are never more evident.
A group of statements, some of which purportedly provide support for another. The statements which purportedly provide the support are the premisses while the statement purportedly support is the conclusion. Arguments are typically divided into two categories depending on the degree of support they purportedly provide. Deductive arguments purportedly provide conclusive support for their conclusions while inductively supports the purported provision that inductive arguments purportedly provided only arguments purportedly in the providing probably of support. Some, but not all, arguments succeed in providing support for their conclusions. Successful deductive arguments are valid while successful inductive arguments are valid while successful inductive arguments are strong. An argument is valid just in case if all its premisses are true its conclusion is only probably true. Deductive logic provides methods for ascertaining whether or not an argument is valid whereas, inductive logic provides methods for ascertaining the degree of support the premisses of an argument confer on its conclusion.
Finally, proof, least of mention, is a collection of considerations and reasons that instill and sustain conviction that some proposed theorem - the theorem proved - is not only true, but could not possibly be false. A perceptual observation may instill the conviction that water is cold. But a proof that 2 + 5 = 5 must not only instill the conviction that is true that 2 + 3 = 5, but also that 2 + 3 could not be anything but the digit 5.
Contemporary philosophers of mind have typically supposed (or at least hoped) that the mind can be naturalized -, i.e., that all mental facts have explanations in the terms of natural science. This assumption is shared within cognitive science, which attempts to provide accounts of mental states and processes in terms (ultimately) of features of the brain and central nervous system. In the course of doing so, the various sub-disciplines of cognitive science (including cognitive and computational psychology and cognitive and computational neuroscience) postulate a number of different kinds of structures and processes, many of which are not directly implicated by mental states and processes as commonsensical conceived. There remains, however, a shared commitment to the idea that mental states and processes are to be explained in terms of mental representations.
In philosophy, recent debates about mental representation have centred around the existence of propositional attitudes (beliefs, desires, etc.) and the determination of their contents (how they come to be about what they are about), and the existence of phenomenal properties and their relation to the content of thought and perceptual experience. Within cognitive science itself, the philosophically relevant debates have been focussed on the computational architecture of the brain and central nervous system, and the compatibility of scientific and commonsense accounts of mentality.
Intentional Realists such as Dretske (e.g., 1988) and Fodor (e.g., 1987) note that the generalizations we apply in everyday life in predicting and explaining each other's behaviour (often collectively referred to as 'folk psychology') are both remarkably successful and indispensable. What a person believes, doubts, desires, fears, etc. is a highly reliable indicator of what that person will do. We have no other way of making sense of each other's behaviour than by ascribing such states and applying the relevant generalizations. We are thus committed to the basic truth of commonsense psychology and, hence, to the existence of the states its generalizations refer to. (Some realists, such as Fodor, also hold that commonsense psychology will be vindicated by cognitive science, given that propositional attitudes can be construed as computational relations to mental representations.)
Intentional Eliminativists, such as Churchland, (perhaps) Dennett and (at one time) Stich argue that no such things as propositional attitudes (and their constituent representational states) are implicated by the successful explanation and prediction of our mental lives and behaviour. Churchland denies that the generalizations of commonsense propositional-attitude psychology are true. He (1981) argues that folk psychology is a theory of the mind with a long history of failure and decline, and that it resists incorporation into the framework of modern scientific theories (including cognitive psychology). As such, it is comparable to alchemy and phlogiston theory, and ought to suffer a comparable fate. Commonsense psychology is false, and the states (and representations) it postulates simply don't exist. (It should be noted that Churchland is not an eliminativist about mental representation tout court.
Dennett (1987) grants that the generalizations of commonsense psychology are true and indispensable, but denies that this is sufficient reason to believe in the entities they appear to refer to. He argues that to give an intentional explanation of a system's behaviour is merely to adopt the 'intentional stance' toward it. If the strategy of assigning contentual states to a system and predicting and explaining its behaviour (on the assumption that it is rational -, i.e., that it behaves as it should, given the propositional attitudes it should have in its environment) is successful, then the system is intentional, and the propositional-attitude generalizations we apply to it are true. But there is nothing more to having a propositional attitude than this.
Though he has been taken to be thus claiming that intentional explanations should be construed instrumentally, Dennett (1991) insists that he is a 'moderate' realist about propositional attitudes, since he believes that the patterns in the behaviour and behavioural dispositions of a system on the basis of which we (truly) attribute intentional states to it are objectively real. In the event that there are two or more explanatorily adequate but substantially different systems of intentional ascriptions to an individual, however, Dennett claims there is no fact of the matter about what the system believes (1987, 1991). This does suggest an irrealism at least with respect to the sorts of things Fodor and Dretske take beliefs to be; though it is not the view that there is simply nothing in the world that makes intentional explanations true.
(Davidson 1973, 1974 and Lewis 1974 also defend the view that what it is to have a propositional attitude is just to be interpretable in a particular way. It is, however, not entirely clear whether they intend their views to imply irrealism about propositional attitudes.). Stich (1983) argues that cognitive psychology does not (or, in any case, should not) taxonomies mental states by their semantic properties at all, since attribution of psychological states by content is sensitive to factors that render it problematic in the context of a scientific psychology. Cognitive psychology seeks causal explanations of behaviour and cognition, and the causal powers of a mental state are determined by its intrinsic 'structural' or 'syntactic' properties. The semantic properties of a mental state, however, are determined by its extrinsic properties -, e.g., its history, environmental or intra-mental relations. Hence, such properties cannot figure in causal-scientific explanations of behaviour. (Fodor 1994 and Dretske 1988 are realist attempts to come to grips with some of these problems.) Stich proposes a syntactic theory of the mind, on which the semantic properties of mental states play no explanatory role.
It is a traditional assumption among realists about mental representations that representational states come in two basic varieties (Boghossian 1995). There are those, such as thoughts, which are composed of concepts and have no phenomenal ('what-it's-like') features ('Qualia'), and those, such as sensory experiences, which have phenomenal features but no conceptual constituents. (Non-conceptual content is usually defined as a kind of content that states of a creature lacking concepts but, nonetheless enjoy. On this taxonomy, mental states can represent either in a way analogous to expressions of natural languages or in a way analogous to drawings, paintings, maps or photographs. (Perceptual states such as seeing that something is blue, are sometimes thought of as hybrid states, consisting of, for example, a Non-conceptual sensory experience and a thought, or some more integrated compound of sensory and conceptual components.)
Some historical discussions of the representational properties of mind (e.g., Aristotle 1984, Locke 1689/1975, Hume 1739/1978) seem to assume that Non-conceptual representations - percepts ('impressions'), images ('ideas') and the like - are the only kinds of mental representations, and that the mind represents the world in virtue of being in states that resemble things in it. On such a view, all representational states have their content in virtue of their phenomenal features. Powerful arguments, however, focussing on the lack of generality (Berkeley 1975), ambiguity (Wittgenstein 1953) and non-compositionality (Fodor 1981) of sensory and imaginistic representations, as well as their unsuitability to function as logical (Frége 1918/1997, Geach 1957) or mathematical (Frége 1884/1953) concepts, and the symmetry of resemblance (Goodman 1976), convinced philosophers that no theory of mind can get by with only Non-conceptual representations construed in this way.
Contemporary disagreement over Non-conceptual representation concerns the existence and nature of phenomenal properties and the role they play in determining the content of sensory experience. Dennett (1988), for example, denies that there are such things as Qualia at all; while Brandom (2002), McDowell (1994), Rey (1991) and Sellars (1956) deny that they are needed to explain the content of sensory experience. Among those who accept that experiences have phenomenal content, some (Dretske, Lycan, Tye) argue that it is reducible to a kind of intentional content, while others (Block, Loar, Peacocke) argue that it is irreducible.
The representationalist thesis is often formulated as the claim that phenomenal properties are representational or intentional. However, this formulation is ambiguous between a reductive and a non-deductive claim (though the term 'representationalism' is most often used for the reductive claim). On one hand, it could mean that the phenomenal content of an experience is a kind of intentional content (the properties it represents). On the other, it could mean that the (irreducible) phenomenal properties of an experience determine an intentional content. Representationalists such as Dretske, Lycan and Tye would assent to the former claim, whereas phenomenalists such as Block, Chalmers, Loar and Peacocke would assent to the latter. (Among phenomenalists, there is further disagreement about whether Qualia are intrinsically representational (Loar) or not (Block, Peacocke).
Most (reductive) representationalists are motivated by the conviction that one or another naturalistic explanation of intentionality is, in broad outline, correct, and by the desire to complete the naturalization of the mental by applying such theories to the problem of phenomenalists. (Needless to say, most phenomenalists (Chalmers is the major exception) are just as eager to naturalize the phenomenal - though not in the same way.)
The main argument for representationalism appeals to the transparency of experience. The properties that characterize what it's like to have a perceptual experience are presented in experience as properties of objects perceived: in attending to an experience, one seems to 'see through it' to the objects and properties it is experiences of. They are not presented as properties of the experience itself. If nonetheless they were properties of the experience, perception would be massively deceptive. But perception is not massively deceptive. According to the representationalist, the phenomenal character of an experience is due to its representing objective, non-experiential properties. (In veridical perception, these properties are locally instantiated; in illusion and hallucination, they are not.) On this view, introspection is indirect perception: one comes to know what phenomenal features one's experience has by coming to know what objective features it represents.
In order to account for the intuitive differences between conceptual and sensory representations, representationalists appeal to their structural or functional differences. Dretske (1995), for example, distinguishes experiences and thoughts on the basis of the origin and nature of their functions: an experience of a property 'P' is a state of a system whose evolved function is to indicate the presence of 'P' in the environment; a thought representing the property 'P', on the other hand, is a state of a system whose assigned (learned) function is to calibrate the output of the experiential system. Rey (1991) takes both thoughts and experiences to be relations to sentences in the language of thought, and distinguishes them on the basis of (the functional roles of) such sentences' constituent predicates. Lycan (1987, 1996) distinguishes them in terms of their functional-computational profiles. Tye (2000) distinguishes them in terms of their functional roles and the intrinsic structure of their vehicles: thoughts are representations in a language-like medium, whereas experiences are image-like representations consisting of 'symbol-filled arrays.' (The account of mental images in Tye 1991.)
Phenomenalists tend to make use of the same sorts of features (function, intrinsic structure) in explaining some of the intuitive differences between thoughts and experiences, but they do not suppose that such features exhaust the differences between phenomenal and non-phenomenal representations. For the phenomenalists, it is the phenomenal properties of experiences - Qualia themselves - that constitute the fundamental difference between experience and thought. Peacocke (1992), for example, develops the notion of a perceptual 'scenario' (an assignment of phenomenal properties to coordinates of a three-dimensional egocentric space), whose content is 'correct' (a semantic property) if in the corresponding 'scene' (the portion of the external world represented by the scenario) properties are distributed as their phenomenal analogues are in the scenario.
Another sort of representation championed by phenomenalists (e.g., Block, Chalmers (2003) and Loar (1996)) is the 'phenomenal concept' -, a conceptual/phenomenal hybrid consisting of a phenomenological 'sample' (an image or an occurrent sensation) integrated with (or functioning as) a conceptual component. Phenomenal concepts are postulated to account for the apparent fact (among others) that, as McGinn (1991) puts it, 'you cannot form [introspective] concepts of conscious properties unless you yourself instantiate those properties.' One cannot have a phenomenal concept of a phenomenal property 'P', and, hence, phenomenal beliefs about P, without having experience of 'P', because 'P' it is (in some way) constitutive of the concept of 'P'. (Jackson 1982, 1986 and Nagel 1974.)
Though imagery has played an important role in the history of philosophy of mind, the important contemporary literature on it is primarily psychological. In a series of psychological experiments done in the 1970s (summarized in Kosslyn 1980 and Shepard and Cooper 1982), subjects' response time in tasks involving mental manipulation and examination of presented figures was found to vary in proportion to the spatial properties (size, orientation, etc.) of the figures presented. The question of how these experimental results are to be explained has kindled a lively debate on the nature of imagery and imagination.
Kosslyn (1980) claims that the results suggest that the tasks were accomplished via the examination and manipulation of mental representations that they have spatial properties, i.e., pictorial representations, or images. Others, principally Pylyshyn (1979, 1981, 2003), argue that the empirical facts can be explained in terms exclusively of discursive, or propositional representations and cognitive processes defined over them. (Pylyshyn takes such representations to be sentences in a language of thought.)
The idea that pictorial representations are literally pictures in the head is not taken seriously by proponents of the pictorial view of imagery. The claim is, rather, that mental images represent in a way that is relevantly like the way pictures represent. (Attention has been focussed on visual imagery - hence the designation 'pictorial'; Though of course, there may imagery in other modalities - auditory, olfactory, etc. - as well.)
The distinction between pictorial and discursive representation can be characterized in terms of the distinction between analog and digital representation (Goodman 1976). This distinction has itself been variously understood (Fodor & Pylyshyn 1981, Goodman 1976, Haugeland 1981, Lewis 1971, McGinn 1989), though a widely accepted construal is that analog representation is continuous (i.e., in virtue of continuously variable properties of the representation), while digital representation is discrete (i.e., in virtue of properties a representation either has or doesn't have) (Dretske 1981). (An analog/digital distinction may also be made with respect to cognitive processes. (Block 1983.)) On this understanding of the analog/digital distinction, imaginistic representations, which represent in virtue of properties that may vary continuously (such for being more or less bright, loud, vivid, etc.), would be analog, while conceptual representations, whose properties do not vary continuously (a thought cannot be more or less about Elvis: either it is or it is not) would be digital.
It might be supposed that the pictorial/discursive distinction is best made in terms of the phenomenal/nonphenomenal distinction, but it is not obvious that this is the case. For one thing, there may be nonphenomenal properties of representations that vary continuously. Moreover, there are ways of understanding pictorial representation that presuppose neither phenomenalists nor analogicity. According to Kosslyn (1980, 1982, 1983), a mental representation is 'quasi-pictorial' when every part of the representation corresponds to a part of the object represented, and relative distances between parts of the object represented are preserved among the parts of the representation. But distances between parts of a representation can be defined functionally rather than spatially - for example, in terms of the number of discrete computational steps required to combine stored information about them. (Rey 1981.)
Tye (1991) proposes a view of images on which they are hybrid representations, consisting both of the pictorial and discursive elements. On Tye's account, images are '(labelled) interpreted symbol-filled arrays.' The symbols represent discursively, while their arrangement in arrays has representational significance (the location of each 'cell' in the array represents a specific viewer-centred 2-D location on the surface of the imagined object)
The contents of mental representations are typically taken to be abstract objects (properties, relations, propositions, sets, etc.). A pressing question, especially for the naturalist, is how mental representations come to have their contents. Here the issue is not how to naturalize content (abstract objects can't be naturalized), but, rather, how to provide a naturalistic account of the content-determining relations between mental representations and the abstract objects they express. There are two basic types of contemporary naturalistic theories of content-determination, causal-informational and functional.
Causal-informational theories hold that the content of a mental representation is grounded in the information it carries about what does (Devitt 1996) or would (Fodor 1987, 1990) cause it to occur. There is, however, widespread agreement that causal-informational relations are not sufficient to determine the content of mental representations. Such relations are common, but representation is not. Tree trunks, smoke, thermostats and ringing telephones carry information about what they are causally related to, but they do not represent (in the relevant sense) what they carry information about. Further, a representation can be caused by something it does not represent, and can represent something that has not caused it.
The main attempts to specify what makes a causal-informational state a mental representation are Asymmetric Dependency Theories, the Asymmetric Dependency Theory distinguishes merely informational relations from representational relations on the basis of their higher-order relations to each other: informational relations depend upon representational relations, but not vice-versa. For example, if tokens of a mental state type are reliably caused by horses, cows-on-dark-nights, zebras-in-the-mist and Great Danes, then they carry information about horses, etc. If, however, such tokens are caused by cows-on-dark-nights, etc. because they were caused by horses, but not vice versa, then they represent horses.
According to Teleological Theories, representational relations are those a representation-producing mechanism has the selected (by evolution or learning) function of establishing. For example, zebra-caused horse-representations do not mean zebra, because the mechanism by which such tokens are produced has the selected function of indicating horses, not zebras. The horse-representation-producing mechanism that responds to zebras is malfunctioning.
Functional theories, hold that the content of a mental representation are well grounded in causal computational inferential relations to other mental portrayals other than mental representations. They differ on whether relata should include all other mental representations or only some of them, and on whether to include external states of affairs. The view that the content of a mental representation is determined by its inferential/computational relations with all other representations is holism; the view it is determined by relations to only some other mental states is localisms (or molecularism). (The view that the content of a mental state depends on none of its relations to other mental states is atomism.) Functional theories that recognize no content-determining external relata have been called solipsistic (Harman 1987). Some theorists posit distinct roles for internal and external connections, the former determining semantic properties analogous to sense, the latter determining semantic properties analogous to reference (McGinn 1982, Sterelny 1989)
(Reductive) representationalists (Dretske, Lycan, Tye) usually take one or another of these theories to provide an explanation of the (Non-conceptual) content of experiential states. They thus tend to be externalists, about phenomenological as well as conceptual content. Phenomenalists and non-deductive representationalists (Block, Chalmers, Loar, Peacocke, Siewert), on the other hand, take it that the representational content of such states is (at least in part) determined by their intrinsic phenomenal properties. Further, those who advocate a phenomenology-based approach to conceptual content (Horgan and Tiensen, Loar, Pitt, Searle, Siewert) also seem to be committed to internalist individuation of the content (if not the reference) of such states.
Generally, those who, like informational theorists, think relations to one's (natural or social) surroundings are (at least partially) determinative of the content of mental representations are externalists (e.g., Burge 1979, 1986, McGinn 1977, Putnam 1975), whereas those who, like some proponents of functional theories, think representational content is determined by an individual's intrinsic properties alone, are internalists (or individualists).
This issue is widely taken to be of central importance, since psychological explanation, whether commonsense or scientific, is supposed to be both causal and content-based. (Beliefs and desires cause the behaviours they do because they have the contents they do. For example, the desire that one have a beer and the beliefs that there is beer in the refrigerator and that the refrigerator is in the kitchen may explain one's getting up and going to the kitchen.) If, however, a mental representation's having a particular content is due to factors extrinsic to it, it is unclear how it has that content could determine its causal powers, which, arguably, must be intrinsic. Some who accept the standard arguments for externalism have argued that internal factors determine a component of the content of a mental representation. They say that mental representations have both 'narrow' content (determined by intrinsic factors) and 'wide' or 'broad' content (determined by narrow content plus extrinsic factors). (This distinction may be applied to the sub-personal representations of cognitive science as well as to those of commonsense psychology.
Narrow content has been variously construed. Putnam (1975), Fodor (1982)), and Block (1986) for example, seems to understand it as something like directorial content (i.e., Frégean sense, or perhaps character, à la Kaplan 1989). On this construal, narrow content is context-independent and directly expressible. Fodor (1987) and Block (1986), however, has also characterized narrow content as radically inexpressible. On this construal, narrow content is a kind of proto-content, or content-determinant, and can be specified only indirectly, via specifications of context/wide-content pairings. Both, construe of as a narrow content and are characterized as functions from context to (wide) content. The narrow content of a representation is determined by properties intrinsic to it or its possessor such as its syntactic structure or its intra-mental computational or inferential role or its phenomenology.
Burge (1986) has argued that causation-based worries about externalist individuation of psychological content, and the introduction of the narrow notion, are misguided. Fodor (1994, 1998) has more recently urged that there may be no need to narrow its contentual representations, accountable for reasons of an ordering supply of naturalistic (causal) explanations of human cognition and action, since the sorts of cases they were introduced to handle, viz., Twin-Earth cases and Frége cases, are nomologically either impossible or dismissible as exceptions to non-constrictions and the rigidity as placed on or upon the psychological laws.
The leading contemporary version of the Representational Theory of Mind, the Computational Theory of Mind, claims that the brain is a kind of computer and that mental processes are computations. According to the computational theory of mind, cognitive states are constituted by computational relations to mental representations of various kinds, and cognitive processes are sequences of such states. The computational theory of mind and the representational theory of mind, may by attempting to explain all psychological states and processes in terms of mental representation. In the course of constructing detailed empirical theories of human and animal cognition and developing models of cognitive processes' implementable in artificial information processing systems, cognitive scientists have proposed a variety of types of mental representations. While some of these may be suited to be mental relata of commonsense psychological states, some - so-called 'subpersonal' or 'sub-doxastic' representations - are not. Though many philosophers believe that computational theory of mind can provide the best scientific explanations of cognition and behaviour, there is disagreement over whether such explanations will vindicate the commonsense psychological explanations of prescientific representational theory of mind.
According to Stich's (1983) Syntactic Theory of Mind, for example, computational theories of psychological states should concern themselves only with the formal properties of the objects those states are relations to. Commitment to the explanatory relevance of content, however, is for most cognitive scientists fundamental. That mental processes are computations, which computations are rule-governed sequences of semantically evaluable objects, and that the rules apply to the symbols in virtue of their content, are central tenets of mainstream cognitive science.
Explanations in cognitive science appeal to a many different kinds of mental representation, including, for example, the 'mental models' of Johnson-Laird 1983, the 'retinal arrays,' 'primal sketches' and '2½ -D sketches' of Marr 1982, the 'frames' of Minsky 1974, the 'sub-symbolic' structures of Smolensky 1989, the 'quasi-pictures' of Kosslyn 1980, and the 'interpreted symbol-filled arrays' of Tye 1991 - in addition to representations that may be appropriate to the explanation of commonsense
Psychological states. Computational explanations have been offered of, among other mental phenomena, belief.
The classicists hold that mental representations are symbolic structures, which typically have semantically evaluable constituents, and that mental processes are rule-governed manipulations of them that are sensitive to their constituent structure. The connectionists, hold that mental representations are realized by patterns of activation in a network of simple processors ('nodes') and that mental processes consist of the spreading activation of such patterns. The nodes themselves are, typically, not taken to be semantically evaluable; nor do the patterns have semantically evaluable constituents. (Though there are versions of Connectionism -, 'localist' versions - on which individual nodes are taken to have semantic properties (e.g., Ballard 1986, Ballard & Hayes 1984).) It is arguable, however, that localist theories are neither definitive nor representative of the Conceptionist program.
Classicists are motivated (in part) by properties thought seems to share with language. Jerry Alan Fodor's (1935-), Language of Thought Hypothesis, (Fodor 1975, 1987), according to which the system of mental symbols constituting the neural basis of thought is structured like a language, provides a well-worked-out version of the classical approach as applied to commonsense psychology. According to the language of a thought hypothesis, the potential infinity of complex representational mental states is generated from a finite stock of primitive representational states, in accordance with recursive formation rules. This combinatorial structure accounts for the properties of productivity and systematicity of the system of mental representations. As in the case of symbolic languages, including natural languages (though Fodor does not suppose either that the language of thought hypotheses explains only linguistic capacities or that only verbal creatures have this sort of cognitive architecture), these properties of thought are explained by appeal to the content of the representational units and their combinability into contentual plexuities. That is, the semantics of both language and thought is compositional: the content of a complex representation is determined by the contents of its constituents and their structural configuration.
Connectionists are motivated mainly by a consideration of the architecture of the brain, which apparently consists of layered networks of interconnected neurons. They argue that this sort of architecture is unsuited to carrying out classical serial computations. For one thing, processing in the brain is typically massively parallel. In addition, the elements whose manipulation drive's computation in Conceptionist networks (principally, the connections between nodes) are neither semantically compositional nor semantically evaluable, as they are on the classical approach. This contrast with classical computationalism is often characterized by saying that representation is, with respect to computation, distributed as opposed too local: representation is local if it is computationally basic; and distributed if it is not. (Another way of putting this is to say that for classicists mental representations are computationally atomic, whereas for connectionists they are not.)
Moreover, connectionists argue that information processing as it occurs in Conceptionist networks more closely resembles some features of actual human cognitive functioning. For example, whereas on the classical view learning involves something like hypothesis formation and testing (Fodor 1981), on the Conceptionist model it is a matter of evolving distribution of 'weight' (strength) on the connections between nodes, and typically does not involve the formulation of hypotheses regarding the identity conditions for the objects of knowledge. The Conceptionist network is 'trained up' by repeated exposure to the objects it is to learn to distinguish, though networks are typically required that many more exposures to the objects than do humans, this seems to model at least one feature of this type of human learning quite well.
Further, degradation in the performance of such networks in response to damage is gradual, not sudden as in the case of a classical information processor, and hence more accurately models the loss of human cognitive function as it typically occurs in response to brain damage. It is also sometimes claimed that Conceptionist systems show the kind of flexibility in response to novel situations typical of human cognition - situations in which classical systems are relatively 'brittle' or 'fragile.'
Some philosophers have maintained that Connectionism entails that there are no propositional attitudes. Ramsey, Stich and Garon (1990) have argued that if Conceptionist models of cognition are basically correct, then there are no discrete representational states as conceived in ordinary commonsense psychology and classical cognitive science. Others, however (e.g., Smolensky 1989), hold that certain types of higher-level patterns of activity in a neural network may be roughly identified with the representational states of commonsense psychology. Still others argue that language-of-thought style representation is both necessary in general and realizable within Conceptionist architectures, collect the central contemporary papers in the classicist/Conceptionist debate, and provides useful introductory material as well.
Whereas Stich (1983) accepts that mental processes are computational, but denies that computations are sequences of mental representations, others accept the notion of mental representation, but deny that computational theory of mind provides the correct account of mental states and processes.
Van Gelder (1995) denies that psychological processes are computational. He argues that cognitive systems are dynamic, and that cognitive states are not relations to mental symbols, but quantifiable states of a complex system consisting of (in the case of human beings) a nervous system, a body and the environment in which they are embedded. Cognitive processes are not rule-governed sequences of discrete symbolic states, but continuous, evolving total states of dynamic systems determined by continuous, simultaneous and mutually determining states of the systems components. Representation in a dynamic system is essentially information-theoretic, though the bearers of information are not symbols, but state variables or parameters.
Horst (1996), on the other hand, argues that though computational models may be useful in scientific psychology, they are of no help in achieving a philosophical understanding of the intentionality of commonsense mental states. Computational theory of mind attempts to reduce the intentionality of such states to the intentionality of the mental symbols they are relations to. But, Horst claims, the relevant notion of symbolic content is essentially bound up with the notions of convention and intention. So the computational theory of mind involves itself in a vicious circularity: the very properties that are supposed to be reduced are (tacitly) appealed to in the reduction.
To say that a mental object has semantic properties is, paradigmatically, to say that it may be about, or be true or false of, an object or objects, or that it may be true or false simpliciter. Suppose I think that you took to sniffing snuff. I am thinking about you, and if what I think of you (that they take snuff) is true of you, then my thought is true. According to representational theory of mind such states are to be explained as relations between agents and mental representations. To think that you take snuff is too token in some way a mental representation whose content is that ocelots take snuff. On this view, the semantic properties of mental states are the semantic properties of the representations they are relations to.
Linguistic acts seem to share such properties with mental states. Suppose I say that you take snuff. I am talking about you, and if what I say of you (that they take snuff) is true of them, then my utterance is true. Now, to say that you take snuff is (in part) to utter a sentence that means that you take snuff. Many philosophers have thought that the semantic properties of linguistic expressions are inherited from the intentional mental states they are conventionally used to express. On this view, the semantic properties of linguistic expressions are the semantic properties of the representations that are the mental relata of the states they are conventionally used to express.
It is also widely held that in addition to having such properties as reference, truth-conditions and truth - so-called extensional properties - expressions of natural languages also have intensional properties, in virtue of expressing properties or propositions -, i.e., in virtue of having meanings or senses, where two expressions may have the same reference, truth-conditions or truth value, yet express different properties or propositions (Frége 1892/1997). If the semantic properties of natural-language expressions are inherited from the thoughts and concepts they express (or vice versa, or both), then an analogous distinction may be appropriate for mental representations.
Theories of representational content may be classified according to whether they are atomistic or holistic and according to whether they are externalistic or internalistic, whereby, emphasizing the priority of a whole over its parts. Furthermore, in the philosophy of language, this becomes the claim that the meaning of an individual word or sentence can only be understood in terms of its relation to an indefinitely larger body of language, such as à whole theory, or even a whole language or form of life. In the philosophy of mind a mental state similarly may be identified only in terms of its relations with others. Moderate holism may allow the other things besides these relationships also count; extreme holism would hold that a network of relationships is all that we have. A holistic view of science holds that experience only confirms or disconfirms large bodies of doctrine, impinging at the edges, and leaving some leeway over the adjustment that it requires.
Once, again, in the philosophy of mind and language, the view that what is thought, or said, or experienced, is essentially dependent on aspects of the world external to the mind of the subject. The view goes beyond holding that such mental states are typically caused by external factors, to insist that they could not have existed as they now do without the subject being embedded in an external world of a certain kind. It is these external relations that make up the essence or identify of the mental state. Externalism is thus opposed to the Cartesian separation of the mental from the physical, since that holds that the mental could in principle exist as it does even if there were no external world at all. Various external factors have been advanced as ones on which mental content depends, including the usage of experts, the linguistic, norms of the community. And the general causal relationships of the subject. In the theory of knowledge, externalism is the view that a person might know something by being suitably situated with respect to it, without that relationship being in any sense within his purview. The person might, for example, be very reliable in some respect without believing that he is. The view allows that you can know without being justified in believing that you know.
However, atomistic theories take a representation's content to be something that can be specified independent entity of that representation' s relations to other representations. What the American philosopher of mind, Jerry Alan Fodor (1935-) calls the crude causal theory, for example, takes a representation to be a
cow
- a menial representation with the same content as the word 'cow' - if its tokens are caused by instantiations of the property of being-a-cow, and this is a condition that places no explicit constraints on how
cow
's must or might relate to other representations. Holistic theories contrasted with atomistic theories in taking the relations à representation bears to others to be essential to its content. According to functional role theories, a representation is a
cow
if it behaves like a
cow
should behave in inference.
Internalist theories take the content of a representation to be a matter determined by factors internal to the system that uses it. Thus, what Block (1986) calls 'short-armed' functional role theories are internalist. Externalist theories take the content of a representation to be determined, in part at least, by factors external to the system that uses it. Covariance theories, as well as telelogical theories that invoke an historical theory of functions, take content to be determined by 'external' factors. Crossing the atomist-holistic distinction with the Internalist-externalist distinction.
Externalist theories (sometimes called non-individualistic theories) have the consequence that molecule for molecule identical cognitive systems might yet harbour representations with different contents. This has given rise to a controversy concerning 'narrow' content. If we assume some form of externalist theory is correct, then content is, in the first instance 'wide' content, i.e., determined in part by factors external to the representing system. On the other hand, it seems clear that, on plausible assumptions about how to individuate psychological capacities, internally equivalent systems must have the same psychological capacities. Hence, it would appear that wide content cannot be relevant to characterizing psychological equivalence. Since cognitive science generally assumes that content is relevant to characterizing psychological equivalence, philosophers attracted to externalist theories of content have sometimes attempted to introduce 'narrow' content, i.e., an aspect or kind of content that is equivalent internally equivalent systems. The simplest such theory is Fodor's idea (1987) that narrow content is a function from contents (i.e., from whatever the external factors are) to wide contents.
All the same, what a person expresses by a sentence is often a function of the environment in which he or she is placed. For example, the disease I refer to by the term like 'arthritis', or the kind of tree I refer to as a 'Maple' will be defined by criteria of which I know next to nothing. This raises the possibility of imagining two persons in rather different environments, but in which everything appears the same to each of them. The wide content of their thoughts and sayings will be different if the situation surrounding them is appropriately different: 'situation' may include the actual objects they perceive or the chemical or physical kinds of object in the world they inhabit, or the history of their words, or the decisions of authorities on what counts as an example, of one of the terms they use. The narrow content is that part of their thought which remains identical, through their identity of the way things appear, regardless of these differences of surroundings. Partisans of wide content may doubt whether any content in this sense narrow, partisans of narrow content believer that it is the fundamental notion, with wide content being explicable in terms of narrow content plus context.
Even so, the distinction between facts and values has outgrown its name: it applies not only to matters of fact vs, matters of value, but also to statements that something is, vs. statements that something ought to be. Roughly, factual statements - 'is statements' in the relevant sense - represent some state of affairs as obtaining, whereas normative statements - evaluative, and deontic ones - attribute goodness to something, or ascribe, to an agent, an obligation to act. Neither distinction is merely linguistic. Specifying a book's monetary value is making a factual statement, though it attributes a kind of value. 'That is a good book' expresses a value judgement though the term 'value' is absent (nor would 'valuable' be synonymous with 'good'). Similarly, 'we are morally obligated to fight' superficially expresses a statement, and 'By all indications it ought to rain' makes a kind of ought-claim but the former is an ought-statement, the latter an (epistemic) is-statement.
Theoretical difficulties also beset the distinction. Some have absorbed values into facts holding that all value is instrumental, roughly, to have value is to contribute - in a factual analysable way - to something further which is (say) deemed desirable. Others have suffused facts with values, arguing that facts (and observations) are 'theory-impregnated' and contending that values are inescapable to theoretical choice. But while some philosophers doubt that fact/value distinctions can be sustained, there persists a sense of a deep difference between evaluating, and attributing an obligation and, on the other hand, saying how the world is.
Fact/value distinctions, may be defended by appeal to the notion of intrinsic value, as a thing has in itself and thus independently of its consequences. Roughly, a value statement (proper) is an ascription of intrinsic value, one to the effect that a thing is to some degree good in itself. This leaves open whether ought-statements are implicitly value statements, but even if they imply that something has intrinsic value -, e.g., moral value - they can be independently characterized, say by appeal to rules that provide (justifying) reasons for action. One might also ground the fact value distinction in the attributional (or even motivational) component apparently implied by the making of valuational or deontic judgements: Thus, 'it is a good book, but that is no reason for a positive attribute towards it' and 'you ought to do it, but there is no reason to' seem inadmissible, whereas, substituting, 'an expensive book' and 'you will do it' yields permissible judgements. One might also argue that factual judgements are the kind which are in principle appraisable scientifically, and thereby anchor the distinction on the factual side. This ligne is plausible, but there is controversy over whether scientific procedures are 'value-free' in the required way.
Philosophers differ regarding the sense, if any, in which epistemology is normative (roughly, valuational). But what precisely is at stake in this controversy is no clearly than the problematic fact/value distinction itself. Must epistemologists as such make judgements of value or epistemic responsibility? If epistemology is naturalizable, then even epistemic principles simply articulate under what conditions - say, appropriate perceptual stimulations - a belief is justified, or constitutes knowledge. Its standards of justification, then would be like standards of, e.g., resilience for bridges. It is not obvious, however, that their appropriate standards can be established without independent judgements that, say, a certain kind of evidence is good enough for justified belief (or knowledge). The most plausible view may be that justification is like intrinsic goodness, though it supervenes on natural properties, it cannot be analysed wholly in factual statements.
Thus far, belief has been depicted as being all-or-nothing, however, as a resulting causality for which we have grounds for thinking it true, and, all the same, its acceptance is governed by epistemic norms, and, least of mention, it is partially subject to voluntary control and has functional affinities to belief. Still, the notion of acceptance, like that of degrees of belief, merely extends the standard picture, and does not replace it.
Traditionally, belief has been of epistemological interest in its propositional guise: 'S' believes that 'p', where 'p' is a reposition towards which an agent, 'S' exhibits an attitude of acceptance. Not all belief is of this sort. If I trust you to say, I believer you. And someone may believe in Mr. Radek, or in a free-market economy, or in God. It is sometimes supposed that all belief is 'reducible' to propositional belief, belief-that. Thus, my believing you might be thought a matter of my believing, is, perhaps, that what you say is true, and your belief in free markets or God, is a matter of your believing that free-market economies are desirable or that God exists.
Some philosophers have followed St. Thomas Aquinas (1225-74), in supposing that to believer in God is simply to believer that certain truths hold while others argue that belief-in is a distinctive attitude, on that includes essentially an element of trust. More commonly, belief-in has been taken to involve a combination of propositional belief together with some further attitude.
The moral philosopher Richard Price (1723-91) defends the claim that there are different sorts of belief-in, some, but not all reducible to beliefs-that. If you believer in God, you believer that God exists, that God is good, you believer that God is good, etc. But according to Price, your belief involves, in addition, a certain complex pro-attitude toward its object. Even so, belief-in outruns the evidence for the corresponding belief-that. Does this diminish its rationality? If belief-in presupposes believes-that, it might be thought that the evidential standards for the former must be, at least, as high as standards for the latter. And any additional pro-attitude might be thought to require a further layer of justification not required for cases of belief-that.
Belief-in may be, in general, less susceptible to alternations in the face of unfavourable evidence than belief-that. A believer who encounters evidence against God's existence may remain unshaken in his belief, in part because the evidence does not bear on his pro-attitude. So long as this ids united with his belief that God exists, and reasonably so - in a way that an ordinary propositional belief that would not.
The correlative way of elaborating on the general objection to justificatory externalism challenges the sufficiency of the various externalist conditions by citing cases where those conditions are satisfied, but where the believers in question seem intuitively not to be justified. In this context, the most widely discussed examples have to do with possible occult cognitive capacities, like clairvoyance. Considering the point in application once, again, to reliabilism, the claim is that to think that he has such a cognitive power, and, perhaps, even good reasons to the contrary, is not rational or responsible and therefore not epistemically justified in accepting the belief that result from his clairvoyance, despite the fact that the reliabilist condition is satisfied.
One sort of response to this latter sorts of an objection is to 'bite the bullet' and insist that such believers are in fact justified, dismissing the seeming intuitions to the contrary are latently internalist prejudices. A more widely adopted response attempts to impose additional conditions, usually of a roughly internalist sort, which will rule out the offending example, while stopping far of a full internalism. But, while there is little doubt that such modified versions of externalism can handle particular cases, as well enough to avoid clear intuitive implausibility, the usually problematic cases that they cannot handle, and also whether there is and clear motivation for the additional requirements other than the general internalist view of justification that externalist is committed to reject.
A view in this same general vein, one that might be described as a hybrid of internalism and externalism holds that epistemic justification requires that there is a justificatory factor that is cognitively accessible to the believer in question (though it need not be actually grasped), thus ruling out, e.g., a pure reliabilism. At the same time, however, though it must be objectively true that beliefs for which such a factor is available are likely to be true, in addition, the fact need not be in any way grasped or cognitively accessible to the believer. In effect, of the premises needed to argue that a particular belief is likely to be true, one must be accessible in a way that would satisfy at least weak internalism, the internalist will respond that this hybrid view is of no help at all in meeting the objection and has no belief nor is it held in the rational, responsible way that justification intuitively seems to require, for the believer in question, lacking one crucial premise, still has no reason at all for thinking that his belief is likely to be true.
An alternative to giving an externalist account of epistemic justification, one which may be more defensible while still accommodating many of the same motivating concerns, is to give an externalist account of knowledge directly, without relying on an intermediate account of justification. Such a view will obviously have to reject the justified true belief account of knowledge, holding instead that knowledge is true belief which satisfies the chosen externalist condition, e.g., a result of a reliable process (and perhaps, further conditions as well). This makes it possible for such a view to retain internalist accounts of epistemic justification, though the centrality of that concept to epistemology would obviously be seriously diminished.
Such an externalist account of knowledge can accommodate the commonsense conviction that animals, young children, and unsophisticated adults' posse's knowledge, though not the weaker conviction (if such a conviction does exist) that such individuals are epistemically justified in their beliefs. It is, at least, less vulnerable to internalist counter-examples of the sort discussed, since the intuitions involved there pertain more clearly to justification than to knowledge. What is uncertain is what ultimate philosophical significance the resulting conception of knowledge, for which is accepted or advanced as true or real on the basis of less than conclusive evidence, as can only be assumed to have. In particular, does it have any serious bearing on traditional epistemological problems and on the deepest and most troubling versions of scepticism, which seems in fact to be primarily concerned with justification, and knowledge?`
A rather different use of the terms 'internalism' and 'externalism' have to do with the issue of how the content of beliefs and thoughts is determined: According to an internalist view of content, the content of such intention states depends only on the non-relational, internal properties of the individual's mind or grain, and not at all on his physical and social environment: While according to an externalist view, content is significantly affected by such external factors and suggests a view that appears of both internal and external elements are standardly classified as an external view.
The main argument for externalism derives from the philosophy of language, more specifically from the various phenomena pertaining to natural kind terms, indexicals, etc. that motivate the views that have come to be known as 'direct reference' theories. Such phenomena seem at least to show that the belief or thought content that can be properly attributed to a person is dependant on facts about his environment, e.g., whether he is on Earth or Twin Earth, what is fact pointing at, the classificatory criterion employed by expects in his social group, etc. - not just on what is going on internally in his mind or brain.
An objection to externalist account of content is that they seem unable to do justice to our ability to know the content of our beliefs or thought 'from the inside', simply by reflection. If content is depending on external factors pertaining to the environment, then knowledge of content should depend on knowledge of these factors - which will not in general be available to the person whose belief or thought is in question.
The adoption of an externalist account of mental content would seem to support an externalist account of justification, apart from contentuality, is a belief unaccessible to the believer, then both the justifying statuses of other beliefs in relation to that of the same representation are the status of that content, being totally rationalized by further beliefs for which it will be similarly inaccessible. Thus, contravening the internalist requirement for justification, as an internalist must insist that there are no justification relations of these sorts, that our internally associable content can also not be warranted or as stated or indicated without the deviated departure from a course or procedure or from a norm or standard in showing no deviation from traditionally held methods of justification exacting by anything else: But such a response appears lame unless it is coupled with an attempt to show that the externalised account of content is mistaken.
Except for alleged cases of thing s that are evident for one just by being true, it has often been thought, anything is known must satisfy certain criteria as well as being true. Except for alleged cases of self-evident truths, it is often thought that anything that is known must satisfy certain criteria or standards. These criteria are general principles that will make a proposition evident or just make accepting it warranted to some degree. Common suggestions for this role include position ‘p’, e.g., that 2 + 2 = 4, ‘p’ is evident or, if ‘p’ coheres wit h the bulk of one’s beliefs, ‘p’ is warranted. These might be criteria whereby putative self-evident truths, e.g., that one clearly and distinctly conceive s ‘p’, ‘transmit’ the status as evident they already have without criteria to other proposition s like ‘p’, or they might be criteria whereby purely non-epistemic considerations, e.g., facts about logical connections or about conception that need not be already evident or warranted, originally ‘create’ p’s epistemic status. If that in turn can be ‘transmitted’ to other propositions, e.g., by deduction or induction, there will be criteria specifying when it is.
Nonetheless, of or relating to tradition a being previously characterized or specified to convey an idea indirectly, as an idea or theory for consideration and being so extreme a design or quality and lean towards an ecocatorial suggestion that implicate an involving responsibility that include: (1) if a proposition ‘p’, e.g., that 2 + 2 = 4, is clearly and distinctly conceived, then ‘p’ is evident, or simply, (2) if we can’t conceive ‘p’ to be false, then ‘p’ is evident: Or, (3) whenever are immediately conscious o f in thought or experience, e.g., that we seem to see red, is evident. These might be criteria whereby putative self-evident truth s, e.g., that one clearly and distinctly conceive, e.g., that one clearly and distinctly conceive ‘p’, ‘transmit’ the status as evident they already have for one without criteria to other propositions like ‘p’. Alternatively, they might be criteria whereby epistemic status, e.g., p’s being evident, is originally created by purely non-epistemic considerations, e.g., facts about how ‘p’ is conceived which are neither self-evident is already criterial evident.
The result effect, holds that traditional criteria do not seem to make evident propositions about anything beyond our own thoughts, experiences and necessary truths, to which deductive or inductive criteria ma y be applied. Moreover, arguably, inductive criteria, including criteria warranting the best explanation of data, never make things evident or warrant their acceptance enough to count as knowledge.
Contemporary epistemologists suggest that traditional criteria may need alteration in three ways. Additional evidence may subject even our most basic judgements to rational correction, though they count as evident on the basis of our criteria. Warrant may be transmitted other than through deductive and inductive relations between propositions. Transmission criteria might not simply ‘pass’ evidence on linearly from a foundation of highly evident ‘premisses’ to ‘conclusions’ that are never more evident.
A group of statements, some of which purportedly provide support for another. The statements which purportedly provide the support are the premisses while the statement purportedly support is the conclusion. Arguments are typically divided into two categories depending on the degree of support they purportedly provide. Deductive arguments purportedly provide conclusive support for their conclusions while inductively supports the purported provision that inductive arguments purportedly provided only arguments purportedly in the providing probably of support. Some, but not all, arguments succeed in providing support for their conclusions. Successful deductive arguments are valid while successful inductive arguments are valid while successful inductive arguments are strong. An argument is valid just in case if all its premisses are true its conclusion is only probably true. Deductive logic provides methods for ascertaining whether or not an argument is valid whereas, inductive logic provides methods for ascertaining the degree of support the premisses of an argument confer on its conclusion.
Finally, proof, least of mention, is a collection of considerations and reasons that instill and sustain conviction that some proposed theorem - the theorem proved - is not only true, but could not possibly be false. A perceptual observation may instill the conviction that water is cold. But a proof that 2 + 5 = 5 must not only instill the conviction that is true that 2 + 3 = 5, but also that 2 + 3 could not be anything but the digit 5.
No one has succeeded in replacing this largely psychological characterization of proofs by a more objective characterization. The representations of reconstructions of proofs as mechanical and semiotical derivation in formal-logical systems all but completely fail to capture ‘proofs’ as mathematicians are quite content to give them. For example, formal-logical derivations depend solely on the logical form of the considered proposition, whereas usually proofs depend in large measure on content of propositions other than their logical form
No one has succeeded in replacing this largely psychological characterization of proofs by a more objective characterization. The representations of reconstructions of proofs as mechanical and semiotical derivation in formal-logical systems all but completely fail to capture ‘proofs’ as mathematicians are quite content to give them, fas or example, formal-logical.
The story of human evolution is as much about the development of cultural behaviour as it is about changes in physical appearance. The term culture, in anthropology, traditionally refers to all human creations and activities governed by social customs and rules. It includes elements such as technology, language, and art. Human cultural behaviour depends on the social transfer of information from one generation to the next, which it depends on a sophisticated system of communication, such as language.
The term culture has often been used to distinguish the behaviour of humans from that of other animals. However, some nonhuman animals also appear to have forms of learned cultural behaviours. For instance, different groups of chimpanzees use different techniques to capture termites for food using sticks. Also, in some regions chimps use stones or pieces of wood for cracking open nuts. Chimps in other regions do not practice this behaviour, although their forests have similar nut trees and materials for making tools. These regional differences resemble traditions that people pass from generation to generation. Traditions are a fundamental aspect of culture, and paleoanthropologists assume that the earliest humans also had some types of traditions.
Nonetheless, modern humans differ from other animals, and probably many earlier human species, in that they actively teach each other and can pass on and accumulate unusually large amounts of knowledge. People also have a uniquely long period of learning before adulthood, and the physical and mental capacity for language. Language of all forms, spoken, signed, and written in provides a medium for communicating vast amounts of information, much more than any other animal appears to be able to transmit through gestures and vocalizations.
Scientists have traced the evolution of human cultural behaviour through the study of archaeological artifacts, such as tools, and related evidence, such as the charred remains of cooked food. Artifacts show that throughout much of human evolution, culture has developed slowly. During the Palaeolithic, or early Stone Age, basic techniques for making stone tools changed very little for periods of well more than a million years.
Human fossils also provide information about how culture has evolved and what effects it has had on human life. For example, over the past 30,000 years, the basic anatomy of humans has undergone only one prominent change: The bones of the average human skeleton have become much smaller and thinner. Innovations in the making and use of tools and in obtaining food results of cultural evolution may have led to more efficient and less physically taxing lifestyles, and thus caused changes in the skeleton.
Paleoanthropologists and archaeologists have studied many topics in the evolution of human cultural behaviour. These have included the evolution of (1) social life; (2) subsistence (the acquisition and production of food); (3) the making and using of tools; (4) environmental adaptation; (5) symbolic thought and its expression through language, art, and religion; and (6) the development of agriculture and the rise of civilizations.
One of the first physicals changes in the evolution of humans from apes-a decrease in the size of male canine teeth
- also indicates a change in social relations. Male apes sometimes use their large canines to threaten (or sometimes fight with) other males of their species, usually over access to females, territory, or food. The evolution of small canines in Australopiths implies that males had either developed other methods of threatening each other or become more cooperative. In addition, both male and female Australopiths had small canines, indicating a reduction of sexual dimorphism from that in apes. Yet, although sexual dimorphism in canine size decreased in Australopiths, males were still much larger than females. Thus, male Australopiths might have competed aggressively with each other based on sheer size and strength, and the social life of humans may not have differed much from that of apes until later times.
Scientists believe that several of the most important changes from apelike to characteristically human social life occurred in species of the genus Homo, whose members show even less sexual dimorphism. These changes, which may have occurred at different times, included (1) prolonged maturation of infants, including an extended period during which they required intensive care from their parents; (2) special bonds of sharing and exclusive mating between particular males and females, called pair-bonding; and (3) the focus of social activity at a home base, a safe refuge in a special location known to family or group members.
Humans, who have a large brain, have a prolonged periods of infant development and childhood because the brain takes a long time too mature. Since the Australopiths brain was not much larger than that of a chimp, some scientists think that the earliest humans had a more apelike rate of growth, which is far more rapid than that of modern humans. This view is supported by studies of Australopiths fossils looking at tooth development-a good indicator of overall body development.
In addition, the human brain becomes very large as it develops, so a woman must give birth to a baby at an early stage of development in order for the infant’s head to fit through her birth canal. Thus, human babies require a long period of care to reach a stage of development at which they depend less on their parents. In contrast with a modern female, a female Australopiths could give birth to a baby at an advanced stage of development because its brain would not be too large to pass through the birth canal. The need to give birth early, -and therefore, to provide more infant care-may have evolved around the time of the middle of the Homo’s species, as well for the Homo’s ergaster. This species had a brain significantly larger than that of the Australopiths, but a narrow birth canal.
Pair-bonding, usually of a short duration, occurs in a variety of primate species. Some scientists speculate that prolonged bonds developed in humans along with increased sharing of food. Among primates, humans have a distinct type of food-sharing behaviour. People will delay eating food until they have returned with it to the location of other members of their social group. This type of food sharing may have arisen at the same time as the need for intensive infant care, probably by the time of H. ergaster. By devoting himself to a particular female and sharing food with her, a male could increase the chances of survival for his own offspring.
Humans have lived as foragers for millions of years. Foragers obtain food when and where it is available over a broad territory. Modern-day foragers (also known as hunter-gatherers) such as, the San people in the Kalahari Desert of southern Africa who also set up central campsites, or home bases, and divide work duties between men and women. Women gather readily available plant and animal foods, while men take on the often less successful task of hunting. For most of the time since the ancestors of modern humans diverged from the ancestors of the living great apes, around seven million years ago, all humans on Earth f ed themselves exclusively by hunting wild animals and gathered wild planets, as the Blackfeet still did in thee 19th century. It was only within the last 11,000 years that some peoples turned to what is termed food production: that is, domesticating wild animals and planets and eating the resulting livestock and crops. Today, most people on Earth consume food that they produced themselves or that someone else produced for them. Some current rates of change, within the next decade the few remaining bands of hunter-gatherers will abandon their ways, disintegrate, or die out, thereby ending our million of the years of commitment to the hunter-gatherers lifestyle. Those few peoples who remained hunter-gatherers into the 20th century escaped replacement by food producers because they ere confined to areas not fit for food production, especially deserts and Arctic regions. Within the present decade, even they will have been seduced by the attractions of civilization, settled down under pressure from bureaucrats or missionaries, or succumbed to germs.
Nevertheless, female and male family members and relatives bring together their food to share at their home base. The modern form of the home base, -that also serves as a haven for raising children and caring for the sick and elderly-may have first developed with middle Homo after about 1.7 million years ago. However, the first evidence of hearths and shelters, -common to all modern home bases-comes from only after 500,000 years ago. Thus, a modern form of social life may not have developed until late in human evolution.
Human subsistence refers to the types of food humans eat, the technology used in and methods of obtaining or producing food, and the ways in which social groups or societies organize them for getting, making, and distributing food. For millions of years, humans probably fed on-the-go, much as other primates do. The lifestyle associated with this feeding strategy is generally organized around small, family-based social groups that take advantage of different food sources at different times of year.
The early human diet probably resembled that of closely related primate species. The great apes eat mostly plant foods. Many primates also eat easily obtained animal foods such as insects and bird eggs. Among the few primates that hunt, chimpanzees will prey on monkeys and even small gazelles. The first humans probably also had a diet based mostly on plant foods. In addition, they undoubtedly ate some animal foods and might have done some hunting. Human subsistence began to diverge from that of other primates with the production and use of the first stone tools. With this development, the meat and marrow (the inner, fat-rich tissue of bones) of large mammals became a part of the human diet. Thus, with the advent of stone tools, the diet of early humans became distinguished in an important way from that of apes.
Scientists have found broken and butchered fossil bones of antelopes, zebras, and other comparably sized animals at the oldest archaeological sites, which go on a date from about 2.5 million years ago. With the evolution of late Homo, humans began to hunt even the largest animals on Earth, including mastodons and mammoths, members of the elephant family. Agriculture and the of animals arose only in the recent past, with H. sapiens.
Paleoanthropologists have debated whether early members of the modern human genus were aggressive hunters, peaceful plant gatherers, or opportunistic scavengers. Many scientists once thought that predation and the eating of meat had strong effects on early human evolution. This hunting hypothesis suggested that early humans in Africa survived particularly arid periods by aggressively hunting animals with primitive stone or bone tools. Supporters of this hypothesis thought that hunting and competition with carnivores powerfully influenced the evolution of human social organization and behaviour; Toolmaking; anatomy, such as the unique structure of the human hand; and intelligence.
Beginning in the 1960s, studies of apes cast doubt on the hunting hypothesis. Researchers discovered that chimpanzees cooperate in hunts of at least small animals, such as monkeys. Hunting did not, therefore, entirely distinguish early humans from apes, and therefore hunting alone may not have determined the path of early human evolution. Some scientists instead argued in favour of the importance of food-sharing in early human life. According to a food-sharing hypothesis, cooperation and sharing within family groups, - instead of aggressive hunting-strongly influenced the path of human evolution.
Scientists once thought that archaeological sites as much as two million years old provided evidence to support the food-sharing hypothesis. Some of the oldest archaeological sites were places where humans brought food and stone tools together. Scientists thought that these sites represented home bases, with many social features of modern hunter-gatherers campsites, including the sharing of food between pair-bonded males and females.
A critique of the food-sharing hypothesis resulted from more careful study of animal bones from the early archaeological sites. Microscopic analysis of these bones revealed the marks of human tools and carnivore teeth, showing that both humans and potential predators, such as hyenas, cats, and jackals were active at these sites. This evidence suggested that what scientists had thought were home bases where early humans shared food were in fact food-processing sites that humans abandoned to predators. Thus, evidence did not clearly support the idea of food-sharing among early humans.
The new research also suggested a different view of early human subsistence that early humans scavenged meat and bone marrow from dead animals and did little hunting. According to this scavenging hypothesis, early humans opportunistically took parts of animal carcasses left by predators, and then used stone tools to remove marrow from the bones.
Observations that many animals, such as antelope, often die off in the dry season make the scavenging hypothesis quite plausible. Early Toolmaker would have had plenty of opportunity to scavenge animal fat and meat during dry times of the year. However, other archaeological studies-and a better appreciation of the importance of hunting among chimpanzees-suggest that the scavenging hypothesis is too narrow. Many scientists now believe that early humans both scavenged and hunted. Evidence of carnivore tooth marks on bones cut by early human Toolmaker suggests that the humans scavenged at least the larger of the animals they ate. They also ate a variety of plant foods. Some disagreement remains, however, as to how much early humans relied on hunting, especially the hunting of smaller animals.
Scientists debate when humans first began hunting on a regular basis. For instance, elephant fossils found with tools made by middle Homo once led researchers to the idea that members of this species were hunters of big game. However, the simple association of animal bones and tools at the same site does not necessarily mean that early humans had killed the animals or eaten their meat. Animals may die in many ways, and natural forces can accidentally place fossils next to tools. Recent excavations at Olorgesailie, Kenya, show that H. erectus cut meat from elephant carcasses but give rise of not revealing to whether these humans were regular or specialized hunters.
Humans who lived outside of Africa, -especially in colder temperate climates, -almost necessitated eating more meat than their African counterparts. Humans in temperate Eurasia would have had to learn about which plants they could safely eat, and the number of available plant foods would drop significantly during the winter. Still, although scientists have found very few fossils of edible or eaten plants at early human sites, early inhabitants of Europe and Asia probably did eat plant foods in addition to meat.
Sites that provide the clearest evidence of early hunting include Boxgrove, England, where about 500,000 years ago people trapped a great number of large game animals between a watering hole and the side of a cliff and then slaughtered them. At Schningen, Germany, a site about 400,000 years old, scientists have found wooden spears with sharp ends that were well designed for throwing and probably used in hunting large animals.
Neanderthals and other archaic humans seem to have eaten whatever animals were available at a particular time and place. So, for example, in European Neanderthal sites, the number of bones of reindeer (a cold-weather animal) and red deer (a warm-weather animal) changed depending on what the climate had been like. Neanderthals probably also combined hunting and scavenging to obtain animal protein and fat.
For at least the past 100,000 years, various human groups have eaten foods from the ocean or coast, such as shellfish and some sea mammals and birds. Others began fishing in interior rivers and lakes. Between probably 90,000 and 80,000 years ago people in Katanda, in what is now the Democratic Republic of the Congo, caught large catfish using a set of barbed bone points, the oldest known specialized fishing implements. The oldest stone tips for arrows or spears date from about 50,000 to 40,000 years ago. These technological advances, probably first developed by early modern humans, indicate an expansion in the kinds of foods humans could obtain.
Beginning 40,000 years ago humans began making even more significant advances in hunting dangerous animals and large herds, and in exploiting ocean resources. People cooperated in large hunting expeditions in which they killed great numbers of reindeer, bison, horses, and other animals of the expansive grasslands that existed at that time. In some regions, people became specialists in hunting certain kinds of animals. The familiarity these people had with the animals they hunted appears in sketches and paintings on cave walls, dating from as much as 32,000 years ago. Hunters also used the bones, ivory, and antlers of their prey to create art and beautiful tools. In some areas, such as the central plains of North America that once teemed with a now-extinct type of large bison (Bison occidentalis), hunting may have contributed to the extinction of entire species.
The making and use of tools alone probably did not distinguish early humans from their ape predecessors. Instead, humans made the important breakthrough of using one tool to make another. Specifically, they developed the technique of precisely hitting one stone against another, known as knapping. Stone Toolmaking characterized the period sometimes referred to as the Stone Age, which began at least 2.5 million years ago in Africa and lasted until the development of metal tools within the last 7,000 years (at different times in different parts of the world). Although early humans may have made stone tools before 2.5 million years ago, Toolmaker may not have remained long enough in one spot to leave clusters of tools that an archaeologist would notice today.
The earliest simple form of stone Toolmaking involved breaking and shaping an angular rock by hitting it with a palm-sized round rock known as a hammerstone. Scientists refer to tools made in this way as Oldowan, after Olduvai Gorge in Tanzania, a site from which many such tools have come. The Oldowan tradition lasted for about one million years. Oldowan tools include large stones with a chopping edge, and small, sharp flakes that could be used to scrape and slice. Sometimes Oldowan Toolmaker used anvil stones (flat rocks found or placed on the ground) on which hard fruits or nuts could be broken open. Chimpanzees are known to do this today.
Scientists once thought that Oldowan Toolmaker intentionally produced several different types of tools. It now appears that differences in the shapes of larger tools were some byproducts of detaching flakes from a variety of natural rock shapes. Learning the skill of Oldowan Toolmaking assiduously required observation, but not necessarily instruction or language. Thus, Oldowan tools were simple, and their makers used them for such purposes as cutting up animal carcasses, breaking bones to obtain marrow, cleaning hides, and sharpening sticks for digging up edible roots and tubers.
Oldowan Toolmaker sought out the best stones for making tools and carried them to food-processing sites. At these sites, the Toolmaker would butcher carcasses and eat the meat and marrow, thus avoiding any predators that might return to a kill. This behaviour of bringing food and tools together contrasts with an eat-as-you-go strategy of feeding commonly seen in other primates.
The Acheulean Toolmaking traditions, which began sometime between 1.7 million and 1.5 million years ago, consisted of increasingly symmetrical tools, most of which scientists refer as to hand-axes and cleavers. Acheulean Toolmaker, such as Homo erectus, also worked with much larger pieces of stone than did Oldowan Toolmaker. The symmetry and size of later Acheulean tools show increased planning and design-and thus probably increased intelligence-on the part of the Toolmaker. The Acheulean tradition continued for more than 1.35 million years.
The next significant advances in stone Toolmaking were made by at least 200,000 years ago. One of these methods of Toolmaking, known as the prepared core technique (and Levallois in Europe), involved carefully and exactingly knocking off small flakes around one surface of a stone and then striking it from the side to produce a preformed tool blank, which could then be worked further. Within the past 40,000 years, modern humans developed the most advanced stone Toolmaking techniques. The so-called prismatic-blade core Toolmaking technique involved removing the top from a stone, leaving a flat platform, and then breaking off multiple blades down the sides of the stone. Each blade had a triangular cross-section, giving it excellent strength. Using these blades as blanks, people made exquisitely shaped spearheads, knives, and numerous other kinds of tools. The most advanced stone tools also exhibit distinct and consistent regional differences in style, indicating a high degree of cultural diversity.
Early humans experienced dramatic shifts in their environments over time. Fossilized plant pollen and animal bones, along with the chemistry of soils and sediments, reveal much about the environmental conditions to which humans had to adapt.
By eight million years ago, the continents of the world, which move over very long periods, had come to the positions they now occupy. However, the crust of the Earth has continued to move since that time. These movements have dramatically altered landscapes around the world. Important geological changes that affected the course of human evolution include those in southern Asia that formed the Himalayan mountain chain and the Tibetan Plateau, and those in eastern Africa that formed the Great Rift Valley. The formation of major mountain ranges and valleys led to changes in wind and rainfall patterns. In many areas dry seasons became more pronounced, and in Africa conditions became generally cooler and drier.
By five million years ago, the amount of fluctuation in global climate had increased. Temperature fluctuations became quite pronounced during the Pliocene Epoch (five million to 1.6 million years ago). During this time the world entered a period of intense cooling called an ice age, which began from place to place of 2.8 million years ago. Ice ages cycle through colder phases known as glacial (times when glaciers form) and warmer phases known as interglacial (during which glaciers melt). During the Pliocene, glacial and interglacial each lasted about 40,000 years each. The Pleistocene Epoch (1.6 million to 10,000 years ago), in contrast, had much larger and longer ice age fluctuations. For instance, beginning about 700,000 years ago, these fluctuations repeated roughly every 100,000 years.
Between five million and two million years ago, a mixture of forests, woodlands, and grassy habitats covered most of Africa. Eastern Africa entered a significant drying period around 1.7 million years ago, and after one million years ago large parts of the African landscape turned to grassland. So the early Australopiths and early Homo lived in wooded places, whereas Homo ergaster and H. erectus lived in areas of Africa that were more open. Early human populations encountered many new and different environments when they spread beyond Africa, including colder temperatures in the Near East and bamboo forests in Southeast Asia. By about 1.4 million years ago, populations had moved into the temperate zone of northeast Asia, and by 800,000 years ago they had dispersed into the temperate latitudes of Europe. Although these first excursions to latitudes of 400 north and higher may have occurred during warm climate phases, these populations also must have encountered long seasons of cold weather.
All of these changes, -dramatic shifts in the landscape, changing rainfall and drying patterns, and temperature fluctuations posed challenges to the immediate and long-term survival of early human populations. Populations in different environments evolved different adaptations, which in part explains why more than one species existed at the same time during much of human evolution.
Some early human adaptations to new climates involved changes in physical (anatomical) form. For example, the physical adaptation of having a tall, lean body such as that of H. ergaster, -with lots of skin exposed to cooling winds-would have dissipated heat very well. This adaptation probably helped the species to survive in the hotter, more open environments of Africa around 1.7 million years ago. Conversely, the short, wide bodies of the Neanderthals would have conserved heat, helping them to survive in the ice age climates of Europe and western Asia
Increases in the size and complexity of the brain, however, made early humans progressively better at adapting through changes in cultural behaviour. The largest of these brain-size increases occurred over the past 700,000 years, a period during which global climates and environments fluctuated dramatically. Human cultural behaviour also evolved more quickly during this period, most likely in response to the challenges of coping with unpredictable and changeable surroundings
Humans have always adapted to their environments by adjusting their behaviour. For instance, early Australopiths moved both in the trees and on the ground, which probably helped them survive environmental fluctuations between wooded and more open habitats. Early Homo adapted by making stone tools and transporting their food over long distances, thereby increasing the variety and quantities of different foods they could eat. An expanded and flexible diet would have helped these Toolmaker survive unexpected changes in their environment and food supply
When populations of H. erectus moved into the temperate regions of Eurasia, but they faced new challenges to survival. During the colder seasons they had to either move away or seek shelter, such as in caves. Some of the earliest definitive evidence of cave dwellers dates from around 800,000 years ago at the site of Atapuerca in northern Spain. This site may have been home too early H. heidelbergensis populations. H. erectus also used caves for shelter.
Eventually, early humans learned to control fire and to use it to create warmth, cook food, and protect themselves from other animals. The oldest known fire hearths date from between 450,000 and 300,000 years ago, at sites such as Bilzingsleben, Germany; Verteszöllös, Hungary; and Zhoukoudian (Chou-k’ou-tien), China. African sites as old as 1.6 million to 1.2 million years contain burned bones and reddened sediments, but many scientists find such evidence too ambiguous to prove that humans controlled fire. Early populations in Europe and Asia may also have worn animal hides for warmth during glacial periods. The oldest known bone needles, which indicate the development of sewing and tailored clothing, date from about 30,000 to 26,000 years ago.
Behaviour relates directly to the development of the human brain, and particularly the cerebral cortex, the part of the brain that allows abstract thought, beliefs, and expression through language. Humans communicate through the use of symbols-ways of referring to things, ideas, and feelings that communicate meaning from one individual to another but that need not have any direct connection to what they identify. For instance, a word-one types of symbol-does not usually relate directly or actualized among the things or indexical to its held idea, but by its representation, it has only of itself for being abstractive.
People can also paint abstract pictures or play pieces of music that evoke emotions or ideas, even though emotions and ideas have no form or sound. In addition, people can conceive of and believe in supernatural beings and powers-abstract concepts that symbolize real-world events such as the creation of Earth and the universe, the weather, and the healing of the sick. Thus, symbolic thought lies at the heart of three hallmarks of modern human culture: language, art, and religion.
In language, people creatively join words together in an endless variety of sentences,-each with a noun, verb and with the collective distinction in meanings, according to a set of mental rules, or grammar. Language provides the ability to communicate complex concepts. It also allows people to exchange information about both past and future events, about objects that are not present, and about complex philosophical or technical concepts
Language gives people many adaptive advantages, including the ability to plan, to communicate the location of food or dangers to other members of a social group, and to tell stories that unify a group, such as mythologies and histories. However, words, sentences, and languages cannot be preserved like bones or tools, so the evolution of language is one of the most difficult topics to investigate through scientific study.
It appears that modern humans have an inborn instinct for language. Under normal conditions not developing language is almost impossible for a person, and people everywhere go through the same stages of increasing language skill at about the same ages. While people appear to have inborn genetic information for developing language, they learn specific languages based on the cultures from which they come and the experiences they have in life.
The ability of humans to have language depends on the complex structure of the modern brain, which has many interconnected, specific areas dedicated to the development and control of language. The complexity of the brain structures necessary for language suggests that it probably took a long time to evolve. While paleoanthropologists would like to know when these important parts of the brain evolved, endocasts (inside impressions) of early human skulls do not provide enough detail to show this.
Some scientists think that even the early Australopiths had some ability to understand and use symbols. Support for this view comes from studies with chimpanzees. A few chimps and other apes have been taught to use picture symbols or American Sign Language for simple communication. Nevertheless, it appears that language, -as well as art and religious rituals became vital aspects of human life only during the past 100,000 years, primarily within our own species.
Humans also express symbolic thought through many forms of art, including painting, sculpture, and music. The oldest known object of possible symbolic and artistic value dates from about 250,000 years ago and comes from the site of Berekhat Ram, Israel. Scientists have interpreted this object, a figure carved into a small piece of volcanic rock, as a representation of the outline of a female body. Only a few other possible art objects are known from between 200,000 and 50,000 years ago. These items, from western Europe and usually attributed to Neanderthals, include two simple pendants-a tooth and a bone with bored holes,-and several grooved or polished fragments of tooth and bone.
Sites dating from at least 400,000 years ago contain fragments of red and black pigment. Humans might have used these pigments to decorate bodies or perishable items, such as wooden tools or clothing of animal hides, but this evidence would not have survived to today. Solid evidence of the sophisticated use of pigments for symbolic purposes,-such as in religious rituals comes only from after 40,000 years ago. From early in this period, researchers have found carefully made types of crayons used in painting and evidence that humans burned pigments to create a range of colours.
People began to create and use advanced types of symbolic objects between about 50,000 and 30,000 years ago. Much of this art appears to have been used in rituals-possibly ceremonies to ask spirit beings for a successful hunt. The archaeological record shows a tremendous blossoming of art between 30,000 and 15,000 years ago. During this period people adorned themselves with intricate jewellery of ivory, bone, and stone. They carved beautiful figurines representing animals and human forms. Many carvings, sculptures, and paintings depict stylized images of the female body. Some scientists think such female figurines represent fertility.
Early wall paintings made sophisticated use of texture and colour. The area upon which is now Southern France contains many famous sites of such paintings. These include the caves of Chauvet, which contain art more than 30,000 years old, and Lascaux, in which paintings date from as much as 18,000 years ago. In some cases, artists painted on walls that can be reached only with special effort, such as by crawling. The act of getting to these paintings gives them a sense of mystery and ritual, as it must have to the people who originally viewed them, and archaeologists refer to some of the most extraordinary painted chambers as sanctuaries. Yet no one knows for sure what meanings these early paintings and engravings had for the people who made them.
Graves from Europe and western Asia indicate that the Neanderthals were the first humans to bury their dead. Some sites contain very shallow graves, which group or family members may have dug simply to remove corpses from sight. In other cases it appears that groups may have observed rituals of grieving for the dead or communicating with spirits. Some researchers have claimed that grave goods, such as meaty animal bones or flowers, had been placed with buried bodies, suggesting that some Neanderthal groups might have believed in an afterlife. In a large proportion of Neanderthal burials, the corpse had its legs and arms drawn in close to its chest, which could indicate a ritual burial position.
Other researchers have challenged these interpretations, however. They suggest that perhaps the Neanderthals had practically rather than religious reasons for positioning dead bodies. For instance, a body manipulated into a fetal position would need only a small hole for burial, making the job of digging a grave easier. In addition, the animal bones and flower pollen near corpses could have been deposited by accident or without religious intention.
Many scientists once thought that fossilized bones of cave bears (a now-extinct species of large bear) found in Neanderthal caves indicated that these people had what has been referred to as a cave bear cult, in which they worshipped the bears as powerful spirits. However, after careful study researchers concluded that the cave bears probably died while hibernating and that Neanderthals did not collect their bones or worship them. Considering current evidence, the case for religion among Neanderthals remains controversial.
One of the most important developments in human cultural behaviour occurred when people began to domesticate (control the breeding of) plants and animals. and the advent of agriculture led to the development of dozens of staple crops (foods that forms the basis of an entire diet) in temperate and tropical regions around the world. Almost the entire population of the world today depends on just four of these major crops: wheat, rice, corn, and potatoes.
The growth of farming and animal herding initiated one of the most remarkable changes ever in the relationship between humans and the natural environment. The change first began just 10,000 years ago in the Near East and has accelerated very rapidly since then. It also occurred independently in other places, including areas of Mexico, China, and South America. Since the first of plants and animals, many species over large areas of the planet have come under human control. The overall number of plant and animal species has decreased, while the populations of a few species needed to support large human populations have grown immensely. In areas dominated by people, interactions between plants and animals usually fall under the control of a single species,-Homo sapiens.
The rise of civilizations-the large and complex types of societies in which most people still live today-developed along with surplus food production. People of high status eventually used food surpluses as a way to pay for labour and to create alliances among groups, often against other groups. In this way, large villages could grow into city-states (urban centres that governed them) and eventually empires covering vast territories. With surplus food production, many people could work exclusively in political, religious, or military positions, or in artistic and various skilled vocations. Command of food surpluses also enabled rulers to control labourers, such as in slavery. All civilizations developed based on such hierarchical divisions of status and vocation.
The earliest civilization arose more than 7,000 years ago in Sumer in what is now Iraq. Sumer grew powerful and prosperous by 5,000 years ago, when it entered on the city-state of Ur. The region containing Sumer, known as Mesopotamia, was the same area in which people had first domesticated animals and plants. Other centres of early civilizations include the Nile Valley of Northeast Africa, the Indus. Valley of South Asia, the Yellow River Valley of East Asia, the Oaxaca and Mexico valleys and the Yucatán region of Central America, and the Andean region of South America, China and Inca Empire.
All early civilizations had some common features. Some of these included a bureaucratic political body, a military, a body of religious leadership, large urban centres, monumental buildings and other works of architecture, networks of trade, and food surpluses created through extensive systems of farming. Many early civilizations also had systems of writing, numbers and mathematics, and astronomy (with calendars); road systems; a formalized body of law; and facilities for education and the punishment of crimes. With the rise of civilizations, human evolution entered a phase vastly different from all before which came. Before this time, humans had lived in small, family-entered groups essentially exposed to and controlled by forces of nature. Several thousand years after the rise of the first civilizations, most people now live in societies of millions of unrelated people, all separated from the natural environment by houses, buildings, automobiles, and numerous other inventions and technologies. Culture will continue to evolve quickly and in unforeseen directions, and these changes will, in turn, influence the physical evolution of Homo sapiens and any other human species to come,-attempt to base ethical reasoning on the presumed fact about evolution. The movement is particularly associated with Spencer, the premise that later elements in an evolutionary path are better than earlier ones, the application of the principle then requires seeing western society, laissez faire capitalism, or another object of approval as more evolved than more ‘primitive’ social forms. Neither the principle nor the application commands much respect. The version of evolutionary ethics called ‘social Darwinism, emphasised the struggle for natural selection, and drew the conclusion that we should glorify and help such struggles, usually by enchaining competitive and aggressive relations between people in society, or between societies themselves. More recently subjective matters and opposing physical theories have rethought the relations between evolution and ethics in the light of biological discoveries concerning altruism and kin-selection.
It is, nevertheless, and, least of mention, that Sociobiology (the academic discipline best known through the work of Edward O. Alison who coined the tern in his Sociobiology: the New Synthesise, 1975). The approach to human behaviour is based on the premise that all social behaviour has a biological basis, and seeks to understand that logical basis as to genetic encoding for features that are themselves selected for through evolutionary history. The philosophical problem is essentially of a methodological finding of the criteria for identifying features that are objectively manifest in what they can usefully identify features. For being in the classical epistemology can be usefully explained in this way. and for finding criteria for assessing various genetic stories that might provide useful explanations among the features proposed. These explanations are such that things as male dominance, male promiscuity versus female fidelity, propensities to sympathy and other emotions, seem as the limited altruism characteristics accused of ignoring the influence of environmental and social factors. In moulding people’s characteristics, e.g., at the limit of silliness, by postulating a ‘gene’ for poverty, is, nonetheless, has no need for the approach for committing such errors, since the feature explained sociobiologically may be indexical to environmental considerations: For instance, it may be a propensity to develop some feature in some social or order environment, or even a propensity to develop propensities . . . That man’s problem was to separate genuine explanation from speculatively methodological morally stories, which may or may not identify really selective mechanisms
Scientists are unbiased observers who use the scientific method to confirm conclusively and falsify various theories. These experts have no preconceptions in gathering the data and logically derive theories from these objective observations. One great strength of science is that its self-correcting, because scientists readily abandon theories when their use has been forfeited, and then again they have shown them to be irrational, although many people have accepted such eminent views of science, they are almost completely untrue. Data can neither conclusively confirm nor conclusively falsify theories, there really is no such thing as the scientific method, data become subjective in practice, and scientists have displayed a surprising fierce loyalty to their theories. There have been many misconceptions of what science is and what science is not.
Science, is, and should be the systematic study of anything that breathes, walk of its own locomotion, in a bipedal orthogonality, and has some effectual regard for its own responsibility of Beingness, and, of course, have to some degreeable form in living personal manner. In that others of science can examine, test, and verify. Not-knowing or knowing has derived the word science from the Latin word scribe meaning ‘to know.’ From its beginnings, science has developed into one of the greatest and most influential fields of human endeavour. Today different branches of science investigate almost everything that thumps in the night in that can observe or detect, and science as the whole shape in the way we understand the universe, our planet, ourselves, and other living things.
Science develops through objective analysis, instead of through personal belief. Knowledge gained in science accumulates as time goes by, building to a turn of work through with what has ben foregoing. Some of this knowledge, such as our understanding of numbers, stretches back to the time of ancient civilizations, when scientific thought first began. Other scientific knowledge,-such as our understanding of genes that cause cancer or of quarks (the smallest known building block of matter), dates back to less than fifty years. However, in all fields of science, old or new, researchers use the same systematic approach, known as the scientific method, to add to what governing evolutionary principles have known.
During scientific investigations, scientists put together and compare new discoveries and existing knowledge. Commonly, new discoveries extend what continuing phenomenons have currently accepted, providing further evidence that existing idea are correct. For example, in 1676 the English physicist Robert Hooke discovered those elastic objects, such as metal springs, stretches in proportion to the force that acts on them. Despite all the advances made in physics since 1676, this simple law still holds true.
Scientists use existing knowledge in new scientific investigations to predict how things will behave. For example, a scientist who knows the exact dimensions of a lens can predict how the lens will focus a beam of light. In the same way, by knowing the exact makeup and properties of two chemicals, a researcher can predict what will happen when they combine. Sometimes scientific predictions go much further by describing objects or events those existing object relations have not yet known. An outstanding instance occurred in 1869, when the Russian chemist Dmitry Mendeleyev drew up a periodic table of the elements arranged to illustrate patterns of recurring chemical and physical properties. Mendeleyev used this table to predict the existence and describe the properties of several elements unknown in his day, and when the mysteriousness of science began the possibilities of experimental simplicities in the discovering enactments whose elements, under which for the several years past, the later, predictions were correct.
In science, and only through experimentation can we find the sublime simplicities of our inherent world, however, by this similarity to theoretical implications can we manifest of what can also be made important as when current ideas are shown to be wrong. A classic case of this occurred early in the 20th century, when the German geologist Alfred Wegener suggested that the continents were at once connected, a theory known as continental drift. At the time, most geologists discounted Wegener's ideas, because the Earth's crust may be fixed. However, following the discovery of plate tectonics in the 1960's, in which scientists found that the Earth’s crust is made of moving plates, continental drift became an important part of geology.
Through advances like these, scientific knowledge is constantly added to and refined. As a result, science gives us an ever more detailed insight into the way the world around us works.
For a large part of recorded history, science had little bearing on people's everyday lives. Scientific knowledge was gathered for its own sake, and it had few practical applications. However, with the dawn of the Industrial Revolution in the 18th century, this rapidly changed. Today, science affects the way we live, largely through technology-the use of scientific knowledge for practical purposes.
Some forms of technology have become so well established that forgetting the great scientific achievements that they represent is easy. The refrigerator, for example, owes its existence to a discovery that liquids take in energy when they evaporate, a phenomenon known as latent heat. The principle of latent heat was first exploited in a practical way in 1876, and the refrigerator has played a major role in maintaining public health ever since. The first automobile, dating from the 1880's, used many advances in physics and engineering, including reliable ways of generating high-voltage sparks, while the first computers emerged in the 1940's from simultaneous advances in electronics and mathematics.
Other fields of science also play an important role in the things we use or consume every day. Research in food technology has created new ways of preserving and flavouring what we eat. Research in industrial chemistry has created a vast range of plastics and other synthetic materials, which have thousands of uses in the home and in industry. Synthetic materials are easily formed into complex shapes and can be used to make machine, electrical, and automotive parts, scientific and industrial instruments, decorative objects, containers, and many other items. Alongside these achievements, science has also caused technology that helps save human life. The kidney dialysis machine enables many people to survive kidney diseases that would once have proved fatal, and artificial valves allow sufferers of coronary heart disease to return to active living. Biochemical research is responsible for the antibiotics and vaccinations that protect us from infectious diseases, and for a wide range of other drugs used to combat specific health problems. As a result, the majority of people on the planet now live longer and healthier lives than ever before.
However, scientific discoveries can also have a negative impact in human affairs. Over the last hundred years, some technological advances that make life easier or more enjoyable have proved to have unwanted and often unexpected long-term effects. Industrial and agricultural chemicals pollute the global environment, even in places as remote as Antarctica, and city air is contaminated by toxic gases from vehicle exhausts. The increasing pace of innovation means that products become rapidly obsolete, adding to a rising tide of waste. Most significantly of all, the burning of fossil fuels such as coal, oil, and natural gas releases into the atmosphere carbon dioxide and other substances knew as greenhouse gases. These gases have altered the composition of the entire atmosphere, producing global warming and the prospect of major climate change in years to come.
Science has also been used to develop technology that raises complex ethical questions. This is particularly true in the fields of biology and medicine. Research involving genetic engineering, cloning, and in vitro fertilization gives scientists the unprecedented power to cause new life, or to devise new forms of living things. At the other extreme, science can also generate technology that is deliberately designed to harm or to kill. The fruits of this research include chemical and biological warfare, and nuclear weapons, by far the most destructive weapons that the world has ever known.
Scientific research can be divided into basic science, also known as pure science, and applied science. In basic science, scientists working primarily at academic institutions pursue research simply to satisfy the thirst for knowledge. In applied science, scientists at industrial corporations conduct research to achieve some kind of practical or profitable gain.
In practice, the division between basic and applied science is not always clear-cut. This is because discoveries that initially seem to have no practical use often develop one as time goes away. For example, superconductivity, the ability to conduct electricity with no resistance, was little more than a laboratory curiosity when Dutch physicist Heike Kamerlingh Omnes discovered it in 1911. Today superconducting electromagnets are used in several of important applications, from diagnostic medical equipment to powerful particle accelerators.
Scientists study the origin of the solar system by analysing meteorites and collecting data from satellites and space probes. They search for the secrets of life processes by observing the activity of individual molecules in living cells. They observe the patterns of human relationships in the customs of aboriginal tribes. In each of these varied investigations the questions asked and the means employed to find answers are different. All the inquiries, however, share a common approach to problem solving known as the scientific method. Scientists may work alone or they may collaborate with other scientists. Always, a scientist’s work must measure up to the standards of the scientific community. Scientists submit their findings to science forums, such as science journals and conferences, to subject the findings to the scrutiny of their peers.
Whatever the aim of their work, scientists use the same underlying steps to organize their research: (1) they make detailed observations about objects or processes, either as they occur in nature or as they take place during experiments; (2) they collect and analyse the information observed; and (3) they formulate a hypothesis that explains the behaviour of the phenomena observed.
A scientist begins an investigation by observing an object or an activity. Observations typically involve one or more of the human senses, like hearing, sight, smells, tastes, and touch. Scientists typically use tools to aid in their observations. For example, a microscope helps view objects too small to be seen with the unaided human eye, while a telescope views objects too far away to be seen by the unaided eye.
Scientists typically implement their observation skills to an experiment. An experiment is any kind of trial that enables scientists to control and change at will the conditions under which events occur. It can be something extremely simple, such as heating a solid to see when it melts, or the periodical perception to differences of complexity, such as bouncing a radio signal off the surface of a distant planet. Scientists typically repeat experiments, sometimes many times, in order to be sure that the results were not affected by unforeseen factors.
Most experiments involve real objects in the physical world, such as electric circuits, chemical compounds, or living organisms. However, with the rapid progress in electronics, computer simulations can now carry out some experiments instead. If they are carefully constructed, these simulations or models can accurately predict how real objects will behave.
One advantage of a simulation is that it allows experiments to be conducted without any risks. Another is that it can alter the apparent passage of time, speeding up or slowing natural processes. This enables scientists to investigate things that happen very gradually, such as evolution in simple organisms, or ones that happen almost instantaneously, such as collisions or explosions.
During an experiment, scientists typically make measurements and collect results as they work. This information, known as data, can take many forms. Data may be a set of numbers, such as daily measurements of the temperature in a particular location or a description of side effects in an animal that has been given an experimental drug. Scientists typically use computers to arrange data in ways that make the information easier to understand and analysed data may be arranged into a diagram such as a graph that shows how one quantity (body temperature, for instance) varies in relation to another quantity (days since starting a drug treatment). A scientist flying in a helicopter may collect information about the location of a migrating herd of elephants in Africa during different seasons of a year. The data collected maybe in the form of geographic coordinates that can be plotted on a map to provide the position of the elephant herd at any given time during a year.
Scientists use mathematics to analyse the data and help them interpret their results. The types of mathematical use that include statistics, which is the analysis of numerical data, and probability, which calculates the likelihood that any particular event will occur.
Once an experiment has been carried out, data collected and analysed, scientists look for whatever pattern their results produce and try to formulate a hypothesis that explains all the facts observed in an experiment. In developing a hypothesis, scientists employ methods of induction to generalize from the experiment’s results to predict future outcomes, and deduction to infer new facts from experimental results.
Formulating a hypothesis may be difficult for scientists because there may not be enough information provided by a single experiment, or the experiment’s conclusion may not fit old theories. Sometimes scientists do not have any prior idea of a hypothesis before they start their investigations, but often scientists start out with a working hypothesis that will be proved or disproved by the results of the experiment. Scientific hypotheses can be useful, just as hunches and intuition can be useful in everyday life. Still, they can also be problematic because they tempt scientists, either deliberately or unconsciously, to favour data that support their ideas. Scientists generally take great care to avoid bias, but it remains an ever-present threat. Throughout the history of science, numerous researchers have fallen into this trap, either in the promise of self-advancement that perceive to be the same or that they firmly believe their ideas to be true.
If a hypothesis is borne out by repeated experiments, it becomes a theory-an explanation that seems to fit with the facts consistently. The ability to predict new facts or events is a key test of a scientific theory. In the 17th century German astronomer Johannes Kepler proposed three theories concerning the motions of planets. Kepler’s theories of planetary orbits were confirmed when they were used to predict the future paths of the planets. On the other hand, when theories fail to provide suitable predictions, these failures may suggest new experiments and new explanations that may lead to new discoveries. For instance, in 1928 British microbiologist Frederick Griffith discovered that the genes of dead virulent bacteria could transform harmless bacteria into virulent ones. The prevailing theory at the time was that genes were made of proteins. Nevertheless, studies succeeded by Canadian-born American bacteriologist Oswald Avery and colleagues in the 1930's repeatedly showed that the transforming gene was active even in bacteria from which protein was removed. The failure to prove that genes were composed of proteins spurred Avery to construct different experiments and by 1944 Avery and his colleagues had found that genes were composed of deoxyribonucleic acid (DNA), not proteins.
If other scientists do not have access to scientific results, the research may as well not have had the liberated amounts of time at all. Scientists need to share the results and conclusions of their work so that other scientists can debate the implications of the work and use it to spur new research. Scientists communicate their results with other scientists by publishing them in science journals and by networking with other scientists to discuss findings and debate issues.
In science, publication follows a formal procedure that has set rules of its own. Scientists describe research in a scientific paper, which explains the methods used, the data collected, and the conclusions that can be drawn. In theory, the paper should be detailed enough to enable any other scientist to repeat the research so that the findings can be independently checked.
Scientific papers usually begin with a brief summary, or abstract, that describes the findings that follow. Abstracts enable scientists to consult papers quickly, without having to read them in full. At the end of most papers is a list of citations-bibliographic references that acknowledge earlier work that has been drawn on in the course of the research. Citations enable readers to work backwards through a chain of research advancements to verify that each step is soundly based.
Scientists typically submit their papers to the editorial board of a journal specializing in a particular field of research. Before the paper is accepted for publication, the editorial board sends it out for peer review. During this procedure a panel of experts, or referees, assesses the paper, judging whether or not the research has been carried out in a fully scientific manner. If the referees are satisfied, publication goes ahead. If they have reservations, some of the research may have to be repeated, but if they identify serious flaws, the entire paper may be rejected from publication.
The peer-review process plays a critical role because it ensures high standards of scientific method. However, it can be a contentious area, as it allows subjective views to become involved. Because scientists are human, they cannot avoid developing personal opinions about the value of each other’s work. Furthermore, because referees tend to be senior figures, they may be less than welcoming to new or unorthodox ideas.
Once a paper has been accepted and published, it becomes part of the vast and ever-expanding body of scientific knowledge. In the early days of science, new research was always published in printed form, but today scientific information spreads by many different means. Most major journals are now available via the Internet (a network of linked computers), which makes them quickly accessible to scientists all over the world.
When new research is published, it often acts as a springboard for further work. Its impact can then be gauged by seeing how often the published research appears as a cited work. Major scientific breakthroughs are cited thousands of times a year, but at the other extreme, obscure pieces of research may be cited rarely or not at all. However, citation is not always a reliable guide to the value of scientific work. Sometimes a piece of research will go largely unnoticed, only to be rediscovered in subsequent years. Such was the case for the work on genes done by American geneticist Barbara McClintock during the 1940s. McClintock discovered a new phenomenon in corn cells known as ‘transposable genes’, sometimes referred to as jumping genes. McClintock observed that a gene could move from one chromosome to another, where it would break the second chromosome at a particular site, insert itself there, and influence the function of an adjacent gene. Her work was largely ignored until the 1960s when scientists found that transposable genes were a primary means for transferring genetic material in bacteria and more complex organisms. McClintock was awarded the 1983 Nobel Prize in physiology or medicine for her work in transposable genes, more than thirty-five years after doing the research.
In addition to publications, scientists form associations with other scientists from particular fields. Many scientific organizations arrange conferences that bring together scientists to share new ideas. At these conferences, scientists present research papers and discuss their implications. In addition, science organizations promote the work of their members by publishing newsletters and Web sites; networking with journalists at newspapers, magazines, and television stations to help them understand new findings; and lobbying lawmakers to promote government funding for research.
The oldest surviving science organization is the Academia dei Lincei, in Italy, which was established in 1603. The same century also saw the inauguration of the Royal Society of London, founded in 1662, and the Académie des Sciences de Paris, founded in 1666. American scientific societies date back to the 18th century, when American scientist and diplomat Benjamin Franklin founded a philosophical club in 1727. In 1743 this organization became the American Philosophical Society, which still exists today.
In the United States, the American Association for the Advancement of Science (AAAS) plays a key role in fostering the public understanding of science and in promoting scientific research. Founded in 1848, it has nearly 300 affiliated organizations, many of which originally developed from AAAS special-interest groups.
Since the late 19th century, communication among scientists has also been improved by international organizations, such as the International Bureau of Weights and Measures, founded in 1873, the International Council of Research, founded in 1919, and the World Health Organization, founded in 1948. Other organizations act as international forums for research in particular fields. For example, the Intergovernmental Panel on Climate Change (IPCC), established in 1988, as research on how climate change occurs, and what affects change is likely to have on humans and their environment.
Classifying sciences involves arbitrary decisions because the universe is not easily split into separate compartments. This article divides science into five major branches: mathematics, physical sciences, earth sciences, life sciences, and social sciences. A sixth branch, technology, draws on discoveries from all areas of science and puts them to practical use. Each of these branches itself consists of numerous subdivisions. Many of these subdivisions, such as astrophysics or biotechnology, combine overlapping disciplines, creating yet more areas of research.
The 20th century mathematics made rapid advances on all fronts. The foundations of mathematics became more solidly grounded in logic, while at the same time mathematics advanced the development of symbolic logic. Philosophy was not the only field to progress with the help of mathematics. Physics, too, benefited from the contributions of mathematicians to relativity theory and quantum theory. In fact, mathematics achieved broader applications than ever before, as new fields developed within mathematics (computational mathematics, game theory, and chaos theory) and other branches of knowledge, including economics and physics, achieved firmer grounding through the application of mathematics. Even the most abstract mathematics seemed to find application, and the boundaries between pure mathematics and applied mathematics grew ever fuzzier Mathematicians searched for unifying principles and general statements that applied to large categories of numbers and objects. In algebra, the study of structure continued with a focus on structural units called rings, fields, and groups, and at mid-century it extended to the relationships between these categories. Algebra became an important part of other areas of mathematics, including analysis, number theory, and topology, as the search for unifying theories moved ahead. Topology—the studies of the properties of objects that remain constant during transformation, or stretching-became a fertile research field, bringing together geometry, algebra, and analysis. Because of the abstract and complex nature of most 20th-century mathematics, most of the remaining sections of this article will discuss practical developments in mathematics with applications in more familiar fields.
Until the 20th century the centres of mathematics research in the West were all located in Europe. Although the University of Göttingen in Germany, the University of Cambridge in England, the French Academy of Sciences and the University of Paris, and the University of Moscow in Russia retained their importance, the United States rose in prominence and reputation for mathematical research, especially the departments of mathematics at Princeton University and the University of Chicago.
At the Second International Congress of Mathematicians held in Paris in 1900, German mathematician David Hilbert spoke to the assembly. Hilbert was a professor at the University of Göttingen, the former academic home of Gauss and Riemann. Hilbert’s speech at Paris was a survey of twenty-three mathematical problems that he felt would guide the work being done in mathematics during the coming century. These problems stimulated a great deal of the mathematical research of the 20th century, and many of the problems were solved. When news breaks that another ‘Hilbert problem’ has been solved, mathematicians worldwide impatiently await further details.
Hilbert contributed to most areas of mathematics, starting with his classic Grundlagen der Geometric (Foundations of Geometry), published in 1899. Hilbert’s work created the field of functional analysis (the analysis of functions as a group), a field that occupied many mathematicians during the 20th century. He also contributed to mathematical physics. From 1915 on he fought to have Emmy Noether, a noted German mathematician, hired at Göttingen. When the university refused to hire her because of objections to the presence of a woman in the faculty senate, Hilbert countered that the senate was not the changing room for a swimming pool. Noether later made major contributions to ring theory in algebra and wrote a standard text on abstract algebra.
In some ways pure mathematics became more abstract in the 20th century, as it joined forces with the field of symbolic logic in philosophy. The scholars who bridged the fields of mathematics and philosophy early in the century were Alfred North Whitehead and Bertrand Russell, who worked together at Cambridge University. They published their major work, Principia Mathematica (Principles of Mathematics), in three volumes from 1910 to 1913. In it they demonstrated the principles of mathematical logic and attempted to show that all of the mathematics could be deduced from a few premises and definitions by the rules of formal logic. In the late 19th century, German mathematician Gottlob Frége had provided the system of notation for mathematical logic and paved the way for the work of Russell and Whitehead. Mathematical logic influenced the direction of 20th-century mathematics, including the work of Hilbert.
Hilbert proposed that the underlying consistency of all mathematics could be demonstrated within mathematics. Nevertheless, logician Kurt Gödel in Austria proved that the goal of establishing the completeness and consistency of every mathematical theory is impossible. Despite its negative conclusion Gödel’s Theorem, published in 1931, opened new areas in mathematical logic. One area, known as recursion theory, played a major role in the development of computers.
Several revolutionary theories, including relativity and quantum theory, challenged existing assumptions in physics in the early 20th century. The work of a number of mathematicians contributed to these theories. Among them was Noether, whose gender had denied her a paid position at the University of Göttingen. Noether’s mathematical formulations on invariant (quantities that remain unchanged as other quantities change) contributed to Einstein’s theory of relativity. Russian mathematician Hermann Minkowski contributed to relativity the notion of the space-time continuum, with time as a fourth dimension. Hermann Weyl, a student of Hilbert’s, investigated the geometry of relativity and applied group theory to quantum mechanics. Weyl’s investigations helped advance the field of topology. Early in the century Hilbert quipped, “Physics is getting too difficult for physicists.”
Hungarian-born American mathematician John von Neumann built a solid mathematical basis for quantum theory with his text Mathematische Grundlagen der Quantenmechanik (1932, Mathematical Foundations of Quantum Mechanics). This investigation led him to explore algebraic operators and groups associated with them, opening a new area now known as Neumann algebra. Von Neumann, however, is probably best known for his work in game theory and computers.
During World War II (1939-1945) mathematicians and physicists worked together on developing radar, the atomic bomb, and other technology that helped defeat the Axis powers. Polish-born mathematician Stanislaw Ulam solved the problem of how to initiate fusion in the hydrogen bomb. Von Neumann participated in numerous US defence projects during the war.
Mathematics plays an important role today in cosmology and astrophysics, especially in research into big bang theory and the properties of black holes, antimatter, elementary particles, and other unobservable objects and events. Stephen Hawking, among the best-known cosmologists of the 20th century, in 1979 was appointed Lucasian Professor of Mathematics at Trinity College, Cambridge, a position once held by Newton.
Mathematics formed an alliance with economics in the 20th century as the tools of mathematical analysis, algebra, probability, and statistics illuminated economic theories. A specialty called econometrics links enormous numbers of equations to form mathematical models for use as forecasting tools.
Game theory began in mathematics but had immediate applications in economics and military strategy. This branch of mathematics deals with situations in which some sort of decision must be made to maximize a profit-that is, too win. Its theoretical foundations were supplied by von Neumann in a series of papers written during the 1930s and 1940s. Von Neumann and economist Oskar Morgenstern published results of their investigations in The Theory of Games and Economic Behaviour (1944). John Nash, the Princeton mathematician profiled in the motion picture A Beautiful Mind, shared the 1994 Nobel Prize in economics for his work in game theory.
Mathematicians, physicists, and engineers contributed to the development of computers and computer science. Nevertheless, the early, theoretical work came from mathematicians. English mathematician Alan Turing, working at Cambridge University, introduced the idea of a machine that could considerably equate of equal value the mathematical operations and solve equations. The Turing machine, as it became known, was a precursor of the modern computer. Through his work Turing brought together the elements that form the basis of computer science: symbolic logic, numerical analysis, electrical engineering, and a mechanical vision of human thought processes.
Computer theory is the third area with which von Neumann is associated, in addition to mathematical physics and game theory. He established the basic principles on which computers operate. Turing and von Neumann both recognized the usefulness of the binary arithmetic system for storing computer programs.
The first large-scale digital computers were pioneered in the 1940s. Von Neumann completed the EDVAC (Electronic Discrete Variable Automatic Computer) at the Institute of Advanced Study in Princeton in 1945. Engineers John Eckert and John Mauchly built ENIAC (Electronic Numerical Integrator and Calculator), which began operation at the University of Pennsylvania in 1946. As increasingly complex computers are built, the field of artificial intelligence has drawn attention. Researchers in this field attempt to develop computer systems that can mimic human thought processes.
Mathematician Norbert Wiener, working at the Massachusetts Institute of Technology (MIT), also became interested in automatic computing and developed the field known as cybernetics. Cybernetics grew out of Wiener’s work on increasing the accuracy of bombsights during World War II. From this came a broader investigation of how information can be translated into improved performance. Cybernetics is now applied to communication and control systems in living organisms.
Computers have exercised an enormous influence on mathematics and its applications. As ever more complex computers are developed, their applications proliferate. Computers have given great impetus to areas of mathematics such as numerical analysis and finite mathematics. Computer science has suggested new areas for mathematical investigation, such as the study of algorithms. Computers also have become powerful tools in areas as diverse as number theory, differential equations, and abstract algebra. In addition, the computer has made possible the solution of several long-standing problems in mathematics, such as the four-colours theorem first proposed in the mid-19th century.
The four-colour theorem stated that four colours are sufficient to colour any map, given that any two countries with a contiguous boundary require different colours. Mathematicians at the University of Illinois finally confirmed the theorem in 1976 by means of a large-scale computer that reduced the number of possible maps too less than 2,000. The program they wrote ran thousands of lines in length and took more than 1,200 hours to run. Many mathematicians, however, do not accept the result as a proof because it has not been checked. Verification by hand would require far too many human hours. Some mathematicians object to the solution’s lack of elegance. This complaint has been paraphrased, “a good mathematical proof is like a poem-this are a telephone directory."
Hilbert inaugurated the 20th century by proposing twenty-three problems that he expected to occupy mathematicians for the next 100 years. A number of these problems, such as the Riemann hypothesis about prime numbers, remain unsolved in the early 21st century. Hilbert claimed, “If I were to awaken after having slept for a thousand years, my first question would be: Has the Riemann hypothesis been proven?”
The existence of old problems, along with new problems that continually arise, ensures that mathematics research will remain challenging and vital through the 21st century. Influenced by Hilbert, the Clay Mathematics Institute at Harvard University announced the Millennium Prize in 2000 for solutions to mathematics problems that have long resisted solution. Among the seven problems is the Riemann hypothesis. An award of $1 million awaits the mathematician who solves any of these problems.
Minkowski, Hermann (1864-1909), Russian mathematician, who developed the concept of the space-time continuum. He was born in Russia and attended and then taught at German universities. To the three dimensions of space, Minkowski added the concept of a fourth dimension, time. This concept developed from Albert Einstein's 1905 relativity theory, and became, in turn, the framework for Einstein's 1916 general theory of relativity.
Gravitation is one of the four fundamental forces of nature, along with electromagnetism and the weak and strong nuclear forces, which hold together the particles that make up atoms. Gravitation is by far the weakest of these forces and, as a result, is not important in the interactions of atoms and nuclear particles or even of moderate-sized objects, such as people or cars. Gravitation is important only when very large objects, such as planets, are involved. This is true for several reasons. First, the force of gravitation reaches great distances, while nuclear forces operate only over extremely short distances and decrease in strength very rapidly as distance increases. Second, gravitation is always attractive. In contrast, electromagnetic forces between particles can be repulsive or attractive depending on whether the particles both have a positive or negative electrical charge, or they have opposite electrical charges. These attractive and repulsive forces tend to cancel each other out, leaving only a weak net force. Gravitation has no repulsive force and, therefore, no such cancellation or weakening.
After presenting his general theory of relativity in 1915, German-born American physicist Albert Einstein tried in vain to unify his theory of gravitation with one that would include all the fundamental forces in nature. Einstein discussed his special and general theories of relativity and his work toward a unified field theory in a 1950 Scientific American article. At the time, he was not convinced that he had discovered a valid solution capable of extending his general theory of relativity to other forces. He died in 1955, leaving this problem unsolved. open sidebar.
Gravitation plays a crucial role in most processes on the earth. The ocean tides are caused by the gravitational attraction of the moon and the sun on the earth and its oceans. Gravitation drives whether patterns by making cold air sink and displace less dense warm air, forcing the warm air to rise. The gravitational pull of the earth on all objects holds the objects to the surface of the earth. Without it, the spin of the earth would send them floating off into space.
The gravitational attraction of every bit of matter in the earth for every other bit of matter amounts to an inward pull that holds the earth together against the pressure forces tending to push it outward. Similarly, the inward pull of gravitation holds stars together. When a star's fuel nears depletion, the processes producing the outward pressure weaken and the inward pull of gravitation eventually compresses the star to a very compact size.
Freefall Falling objects accelerate in response to the force exerted on them by Earth’s gravity. Different objects accelerate at the same rate, regardless of their mass. This illustration shows the speed at which a ball and a cat would be moving and the distance each would have fallen at intervals of a tenth of a second during a short fall
If an object held near the surface of the earth is released, it will fall and accelerate, or pick up speed, as it descends. This acceleration is caused by gravity, the force of attraction between the object and the earth. The force of gravity on an object is also called the object's weight. This force depends on the object's mass, or the amount of matter in the object. The weight of an object is equal to the mass of the object multiplied by the acceleration due to gravity.
A bowling ball that weighs 16 lb. is being pulled toward the earth with a force of 16 lb? In the metric system, the bowling ball is pulled toward the earth with a force of seventy-one newtons (a metric unit of force abbreviated N). The bowling ball also pulls on the earth with a force of 16 lb. (71 N), but the earth is so massive that it does not move appreciably. In order to hold the bowling ball up and keep it from falling, a person must exert an upward force of 16 lb (71 N) on the ball. This upward force acts to oppose the 16 lb. (71 N) downward weight force, leaving a total force of zero. The total force on an object determines the object's acceleration.
If the pull of gravity is the only force acting on an object, then all objects, regardless of their weight, size, or shape, will accelerate in the same manner. At the same place on the earth, the 16 lb. (71 N) bowling ball and a 500 lb. (2200 N) boulder will fall with the same rate of acceleration. As each second passes, each object will increase its downward speed by about 9.8 m. sec.(thirty-two ft./sec.), resulting in an acceleration of 9.8 m/sec/sec (32 ft. sec/sec). In principle, a rock and a feather both would fall with this acceleration if there were no other forces acting. In practice, however, air friction exerts a greater upward force on the falling feather than on the rock and makes the feather fall more slowly than the rock.
The mass of an object does not change as it is moved from place to place, but the acceleration due to gravity, and therefore the object's weight, will change because the strength of the earth's gravitational pull is not the same everywhere. The earth's pull and the acceleration due to gravity decrease as an object moves farther away from the centre of the earth. At an altitude of 4000 miles (6400 km) above the earth's surface, for instance, the bowling ball that weighed 16 lb (71 N) at the surface would weigh only about 4 lb. (18 N). Because of the reduced weight force, the rate of acceleration of the bowling ball at that altitude would be only one quarter of the acceleration rate at the surface of the earth. The pull of gravity on an object also changes slightly with latitude. Because the earth is not perfectly spherical, but bulges at the equator, the pull of gravity is about 0.5 percent stronger at the earth's poles than at the equator.
The special theory of relativity dealt only with constant, as opposed to accelerated, motion of the frames of reference, and the Lorentz transformations apply to frames moving with uniform motion with respect to each other. In 1915-1916, Einstein extended relativity to account for the more general case of accelerated frames of reference. Of Albert Einstein’s general theory of relativity, the central idea in general relativity theory, which accounts for accelerated motion, is that distinguishing between the effects of gravity is impossible and of nonuniform motion. If we did not know, for example, that we were on a spacecraft accelerating at a constant speed and dropped a cup of coffee, we cold not determined whether the mess on the floor was due to the effects of gravity or the accelerated motion, this inability to distinguish between an apparent nonuniform motion, like an acceleration, and gravity is known as the ‘principle of equivalence’.
In this context, Einstein posited the laws elating space and time measurements carried out by two observers moving uniformly, as of one observer in an accelerating spacecraft and another on Earth. Force fields, like gravity, causes the space-like semiotic force, Einstein concluded, to become warped or curved and hence non-Euclidean in form. In the general theory the motion of material points, including light, is not along straight lines, as in Euclidean space, but along geodesics was confirmed in an experiment performed during a total eclipse of the Sun by Arthur Eddington in 1919.
Here, as in the special theory, visualization may help to understand the situation but does not really describe it. This is nicely illustrated in the typical visual analogy used to illustrate what spatial geodesic’ is based. In this tremendous sheet of paper, extends infinitely in all directions. The inhabitants of this flatland, the flat landers, are not only aware of the third dimension. Since the world here is perfectly Euclidean, any measurement of the sum of lines, no mater how far expended, would never meet.
We are then asked to mov e our flat landers to a new land on the surface of a large sphere. Initially, our relocated population would perceive their new world as identical to the old, or as Euclidean and flat. Next we suppose them to send a kind of laser light along the surface of their two world for thousands of mile s. the discovery is then made that if the two beams of light are sent in parallel directions, the come together after travelling a thousand miles.
After experiencing utter confusion in the face of these results, the flatlaners eventually realize that their world is non-Euclidean or curved and invert Riemannian geometry to describe the curved space. The analogy normally concludes with the suggestion that we are the flatlanders, with the difference being that our story takes place in three, rather than two, dimensions in space. Just as the shadow creatures could not visualize the curved two-dimensional surface of their world, so we cannot visualize a three-dimensional curved space.
Thus a visual analogy to illustrate the reality described by the general theory is useful only to the extent that it entices us into an acceptance of the proposition that the reality is unvisualizable. Yet here, as in the special theory, there is no ambiguity in the mathematical description of this reality. Although curved geodesics are not any more unphysical than straight lines, visualizing the three spatial dimensions as a ‘surface’ in’ in the higher four-dimensional space-time cannot be done. Visualization may help us better understand what is implied by the general theory, but it does not disclose what is really meant by the theory,
The ancient Greek philosophers developed several theories about the force that caused objects to fall toward the earth. In the 4th century Bc, the Greek philosopher Aristotle proposed that all things were made from some combination of the four elements, earth, air, fire, and water. Objects that were similar in nature attracted one another, and as a result, objects with more earth in them were attracted to the earth. Fire, by contrast, was dissimilar and therefore tended to rise from the earth. Aristotle also developed a cosmology, that is, a theory describing the universe, that was geocentric, or earth-entered, with the moon, sun, planets, and stars moving around the earth on spheres. The Greek philosophers, however, did not propose a connection between the force behind planetary motion and the force that made objects fall toward the earth.
At the beginning of the 17th century, the Italian physicist and astronomer Galileo discovered that all objects fall toward the earth with the same acceleration, regardless of their weight, size, or shape, when gravity is the only force acting on them. Galileo also had a theory about the universe, which he based on the ideas of the Polish astronomer Nicolaus Copernicus. In the mid-16th century, Copernicus had proposed a heliocentric, or sun-centred system, in which the planets moved in circles around the sun, and Galileo agreed with this cosmology. However, Galileo believed that the planets moved in circles because this motion was the natural path of a body with no forces acting on it. Like the Greek philosophers, he saw no connection between the force behind planetary motion and gravitation on earth.
In the late 16th and early 17th centuries the heliocentric model of the universe gained support from observations by the Danish astronomer Tycho Brahe, and his student, the German astronomer Johannes Kepler. These observations, made without telescopes, were accurate enough to determine that the planets did not move in circles, as Copernicus had suggested. Kepler calculated that the orbits had to be ellipses (slightly elongated circles). The invention of the telescope made even more precise observations possible, and Galileo was one of the first to use a telescope to study astronomy. In 1609 Galileo observed that moons orbited the planet Jupiter, a fact that could not presumably fit into an earth-centred model of the heavens.
The new heliocentric theory changed scientists' views about the earth's place in the universe and opened the way for new ideas about the forces behind planetary motion. However, it was not until the late 17th century that Isaac Newton developed a theory of gravitation that encompassed both the attraction of objects on the earth and planetary motion.
Gravitational forces because the Moon has significantly less mass than Earth, the weight of an object on the Moon’s surface is only one-sixth the object’s weight on Earth’s surface. This graph shows how much and object that weigh on Earth would weigh at different points between the Earth and Moon. Since the Earth and Moon pull in opposite directions, there is a point, about 346,000 km (215,000 mi) from Earth, where the opposite gravitational forces would cancel, and the object's weight would be zero.
To develop his theory of gravitation, Newton first had to develop the science of forces and motion called mechanics. Newton proposed that the natural motion of an object be motion at a constant speed on a straight line, and that it takes a force too slow, speed, or change the path of an object. Newton also invented calculus, a new branch of mathematics that became an important tool in the calculations of his theory of gravitation.
Newton proposed his law of gravitation in 1687 and stated that every particle in the universe attracts every other particle in the universe with a force that depends on the product of the two particles' masses divided by the square of the distance between them. The gravitational force between two objects can be expressed by the following equation: F= GMm/d2 where F is the gravitational force, G is a constant known as the universal constant of gravitation, M and m are the masses of each object, and d is the distance between them. Newton considered a particle to be an object with a mass that was concentrated in a small point. If the mass of one or both particles increases, then the attraction between the two particles increases. For instance, if the mass of one particle is doubled, the force of attraction between the two particles is doubled. If the distance between the particles increases, then the attraction decreases as the square of the distance between them. Doubling the distance between two particles, for instance, will make the force of attraction one quarter as great as it was.
According to Newton, the force acts along a line between the two particles. In the case of two spheres, it acts similar between their centres. The attraction between objects with irregular shapes is more complicated. Every bit of matter in the irregular object attracts every bit of matter in the other object. A simpler description is possible near the surface of the earth where the pull of gravity is approximately uniform in strength and direction. In this case there is a point in an object (even an irregular object) called the centre of gravity, at which all the force of gravity can be considered to be acting.
Newton's law affects all objects in the universe, from raindrops in the sky to the planets in the solar system. It is therefore known as the universal law of gravitation. In order to know the strength of gravitational forces overall, however, it became necessary to find the value of ‘G’, the universal constant of gravitation. Scientists needed to re-enact an experiment, but gravitational forces are very weak between objects found in a common laboratory and thus hard to observe. In 1798 the English chemist and physicist Henry Cavendish finally measured G with a very sensitive experiment in which he nearly eliminated the effects of friction and other forces. The value he found was 6.754 x 10-11 N-m2/kg2-close to the currently accepted value of 6.670 x 10-11 N-m2/kg2 (a decimal point followed by ten zeros and then the number 6670). This value is so small that the force of gravitation between two objects with a mass of 1 metric ton each, 1 metre from each other, is about sixty-seven millionths of a newton, or about fifteen millionths of a pound.
Gravitation may also be described in a completely different way. A massive object, such as the earth, may be thought of as producing a condition in space around it called a gravitational field. This field causes objects in space to experience a force. The gravitational field around the earth, for instance, produces a downward force on objects near the earth surface. The field viewpoint is an alternative to the viewpoint that objects can affect each other across distance. This way of thinking about interactions has proved to be very important in the development of modern physics.
Newton's law of gravitation was the first theory to describe the motion of objects on the earth accurately as well as the planetary motion that astronomers had long observed. According to Newton's theory, the gravitational attraction between the planets and the sun holds the planets in elliptical orbits around the sun. The earth's moon and moons of other planets are held in orbit by the attraction between the moons and the planets. Newton's law led to many new discoveries, the most important of which was the discovery of the planet Neptune. Scientists had noted unexplainable variations in the motion of the planet Uranus for many years. Using Newton's law of gravitation, the French astronomer Urbain Leverrier and the British astronomer John Couch each independently predicted the existence of a more distant planet that was perturbing the orbit of Uranus. Neptune was discovered in 1864, in an orbit close to its predicted position.
Frames of Reference, as only a situation can appear different when viewed from different frames of reference. Try to imagine how an observer's perceptions could change from frame to frame in this illustration.
Scientists used Newton's theory of gravitation successfully for many years. Several problems began to arise, however, involving motion that did not follow the law of gravitation or Newtonian mechanics. One problem was the observed and unexplainable deviations in the orbit of Mercury (which could not be caused by the gravitational pull of another orbiting body).
Another problem with Newton's theory involved reference frames, that is, the conditions under which an observer measures the motion of an object. According to Newtonian mechanics, two observers making measurements of the speed of an object will measure different speeds if the observers are moving relative to each other. A person on the ground observing a ball that is on a train passing by will measure the speed of the ball as the same as the speed of the train. A person on the train observing the ball, however, will measure the ball's speed as zero. According to the traditional ideas about space and time, then, there could not be a constant, fundamental speed in the physical world because all speed is relative. However, near the end of the 19th century the Scottish physicist James Clerk Maxwell proposed a complete theory of electric and magnetic forces that contained just such a constant, which he called c. This constant speed was 300,000 km/sec (186,000 mi/sec) and was the speed of electromagnetic waves, including light waves. This feature of Maxwell's theory caused a crisis in physics because it indicated that speed was not always relative.
Albert Einstein resolved this crisis in 1905 with his special theory of relativity. An important feature of Einstein's new theory was that no particle, and even no information, could travel faster than the fundamental speed c. In Newton's gravitation theory, however, information about gravitation moved at infinite speed. If a star exploded into two parts, for example, the change in gravitational pull would be felt immediately by a planet in a distant orbit around the exploded star. According to Einstein's theory, such forces were not possible.
Though Newton's theory contained several flaws, it is still very practical for use in everyday life. Even today, it is sufficiently accurate for dealing with earth-based gravitational effects such as in geology (the study of the formation of the earth and the processes acting on it), and for most scientific work in astronomy. Only when examining exotic phenomena such as black holes (points in space with a gravitational force so strong that not even light can escape them) or in explaining the big bang (the origin of the universe) is Newton's theory inaccurate or inapplicable.
The gravitational attraction of objects for one another is the easiest fundamental force to observe and was the first fundamental force to be described with a complete mathematical theory by the English physicist and mathematician Sir Isaac Newton. A more accurate theory called general relativity was formulated early in the 20th century by the German-born American physicist Albert Einstein. Scientists recognize that even this theory is not correct for describing how gravitation works in certain circumstances, and they continue to search for an improved theory.
Gravitation plays a crucial role in most processes on the earth. The ocean tides are caused by the gravitational attraction of the moon and the sun on the earth and its oceans. Gravitation drives weather patterns by making cold air sink and displace less dense warm air, forcing the warm air to rise. The gravitational pull of the earth on all objects holds the objects to the surface of the earth. Without it, the spin of the earth would send them floating off into space.
The gravitational attraction of every bit of matter in the earth for every other bit of matter amounts to an inward pull that holds the earth together against the pressure forces tending to push it outward. Similarly, the inward pull of gravitation holds stars together. When a star's fuel nears depletion, the processes producing the outward pressure weaken and the inward pull of gravitation eventually compresses the star to a very compact size.
If the pull of gravity is the only force acting on an object, then all objects, regardless of their weight, size, or shape, will accelerate in the same manner. At the same place on the earth, the 16 lb (71 N) bowling ball and a 500 lb (2200 N) boulder will fall with the same rate of acceleration. As each second passes, each object will increase its downward speed by about 9.8 m/sec (32 ft/sec), resulting in an acceleration of 9.8 m/sec/sec (32 ft/sec/sec). In principle, a rock and a feather both would fall with this acceleration if there were no other forces acting. In practice, however, air friction exerts a greater upward force on the falling feather than on the rock and makes the feather fall more slowly than the rock.
The mass of an object does not change as it is moved from place to place, but the acceleration due to gravity, and therefore the object's weight, will change because the strength of the earth's gravitational pull is not the same everywhere. The earth's pull and the acceleration due to gravity decrease as an object moves farther away from the centre of the earth. At an altitude of 4000 miles (6400 km) above the earth's surface, for instance, the bowling ball that weighed 16 lb (71 N) at the surface would weigh only about 4 lb (18 N). Because of the reduced weight force, the rate of acceleration of the bowling ball at that altitude would be only one quarter of the acceleration rate at the surface of the earth. The pull of gravity on an object also changes slightly with latitude. Because the earth is not perfectly spherical, but bulges at the equator, the pull of gravity is about 0.5 percent stronger at the earth's poles than at the equator.
The ancient Greek philosophers developed several theories about the force that caused objects to fall toward the earth. In the 4th century Bc, the Greek philosopher Aristotle proposed that all things were made from some combination of the four elements, earth, air, fire, and water. Objects that were similar in nature attracted one another, and as a result, objects with more earth in them were attracted to the earth. Fire, by contrast, was dissimilar and therefore tended to rise from the earth. Aristotle also developed a cosmology, that is, a theory describing the universe, that was geocentric, or earth-entered, with the moon, sun, planets, and stars moving around the earth on spheres. The Greek philosophers, however, did not propose a connection between the force behind planetary motion and the force that made objects fall toward the earth.
At the beginning of the 17th century, the Italian physicist and astronomer Galileo discovered that all objects fall toward the earth with the same acceleration, regardless of their weight, size, or shape, when gravity is the only force acting on them. Galileo also had a theory about the universe, which he based on the ideas of the Polish astronomer Nicolaus Copernicus. In the mid-16th century, Copernicus had proposed a heliocentric, or sun-entered system, in which the planets moved in circles around the sun, and Galileo agreed with this cosmology. However, Galileo believed that the planets moved in circles because this motion was the natural path of a body with no forces acting on it. Like the Greek philosophers, he saw no connection between the force behind planetary motion and gravitation on earth.
In the late 16th and early 17th centuries the heliocentric model of the universe gained support from observations by the Danish astronomer Tycho Brahe, and his student, the German astronomer Johannes Kepler. These observations, made without telescopes, were accurate enough to determine that the planets did not move in circles, as Copernicus had suggested. Kepler calculated that the orbits had to be ellipses (slightly elongated circles). The invention of the telescope made even more precise observations possible, and Galileo was one of the first to use a telescope to study astronomy. In 1609 Galileo observed that moons orbited the planet Jupiter, a fact that could not presumably fit into an earth-centred model of the heavens.
The new heliocentric theory changed scientists' views about the earth's place in the universe and opened the way for new ideas about the forces behind planetary motion. However, it was not until the late 17th century that Isaac Newton developed a theory of gravitation that encompassed both the attraction of objects on the earth and planetary motion.
Gravitational Forces Because the Moon has significantly less mass than Earth, the weight of an object on the Moon’s surface is only one-sixth the object’s weight on Earth’s surface. This graph shows how much an object that weighs ‘w’ on Earth would weigh at different points between the Earth and Moon. Since the Earth and Moon pull in opposite directions, there is a point, about 346,000 km (215,000 mi) from Earth, where the opposite gravitational forces would cancel, and the object's weight would be zero.
To develop his theory of gravitation, Newton first had to develop the science of forces and motion called mechanics. Newton proposed that the natural motion of an object be motion at a constant speed on a straight line, and that it takes a force too slow, speed, or change the path of an object. Newton also invented calculus, a new branch of mathematics that became an important tool in the calculations of his theory of gravitation.
Newton proposed his law of gravitation in 1687 and stated that every particle in the universe attracts every other particle in the universe with a force that depends on the product of the two particles' masses divided by the square of the distance between them. The gravitational force between two objects can be expressed by the following equation: F= GMm/d2 where F is the gravitational force, ‘G’ is a constant known as the universal constant of gravitation, ‘M’ and ‘m’ are the masses of each object, and d is the distance between them. Newton considered a particle to be an object with a mass that was concentrated in a small point. If the mass of one or both particles increases, then the attraction between the two particles increases. For instance, if the mass of one particle is doubled, the force of attraction between the two particles is doubled. If the distance between the particles increases, then the attraction decreases as the square of the distance between them. Doubling the distance between two particles, for instance, will make the force of attraction one quarter as great as it was.
According to Newton, the force acts along a line between the two particles. In the case of two spheres, it acts similarly between their centres. The attraction between objects with irregular shapes is more complicated. Every bit of matter in the irregular object attracts every bit of matter in the other object. A simpler description is possible near the surface of the earth where the pull of gravity is approximately uniform in strength and direction. In this case there is a point in an object (even an irregular object) called the centre of gravity, at which all the force of gravity can be considered to be acting.
Newton's law affects all objects in the universe, from raindrops in the sky to the planets in the solar system. It is therefore known as the universal law of gravitation. In order to know the strength of gravitational forces overall, however, it became necessary to find the value of G, the universal constant of gravitation. Scientists needed to re-enact an experiment, but gravitational forces are very weak between objects found in a common laboratory and thus hard to observe. In 1798 the English chemist and physicist Henry Cavendish finally measured ‘G’ with a very sensitive experiment in which he nearly eliminated the effects of friction and other forces. The value he found was 6.754 x 10-11 N-m2/kg2-close to the currently accepted value of 6.670 x 10-11 N-m2/kg2 (a decimal point followed by ten zeros and then the number 6670). This value is so small that the force of gravitation between two objects with a mass of 1 metric ton each, 1 metre from each other, is about sixty-seven millionths of a newton, or about fifteen millionths of a pound.
Gravitation may also be described in a completely different way. A massive object, such as the earth, may be thought of as producing a condition in space around it called a gravitational field. This field causes objects in space to experience a force. The gravitational field around the earth, for instance, produces a downward force on objects near the earth surface. The field viewpoint is an alternative to the viewpoint that objects can affect each other across distance. This way of thinking about interactions has proved to be very important in the development of modern physics.
Newton's law of gravitation was the first theory to describe the motion of objects on the earth accurately as well as the planetary motion that astronomers had long observed. According to Newton's theory, the gravitational attraction between the planets and the sun holds the planets in elliptical orbits around the sun. The earth's moon and moons of other planets are held in orbit by the attraction between the moons and the planets. Newton's law led to many new discoveries, the most important of which was the discovery of the planet Neptune. Scientists had noted unexplainable variations in the motion of the planet Uranus for many years. Using Newton's law of gravitation, the French astronomer Urbain Leverrier and the British astronomer John Couch each independently predicted the existence of a more distant planet that was perturbing the orbit of Uranus. Neptune was discovered in 1864, in an orbit close to its predicted position.
Einstein's general relativity theory predicts special gravitational conditions. The Big Bang theory, which describes the origin and early expansion of the universe, is one conclusion based on Einstein's theory that has been verified in several independent ways.
Another conclusion suggested by general relativity, as well as other relativistic theories of gravitation, is that gravitational effects move in waves. Astronomers have observed a loss of energy in a pair of neutron stars (stars composed of densely packed neutrons) that are orbiting each other. The astronomers theorize that energy-carrying gravitational waves are radiating from the pair, depleting the stars of their energy. Very violent astrophysical events, such as the explosion of stars or the collision of neutron stars, can produce gravitational waves strong enough that they may eventually be directly detectable with extremely precise instruments. Astrophysicists are designing such instruments with the hope that they will be able to detect gravitational waves by the beginning of the 21st century.
Another gravitational effect predicted by general relativity is the existence of black holes. The idea of a star with a gravitational force so strong that light cannot escape from its surface can be traced to Newtonian theory. Einstein modified this idea in his general theory of relativity. Because light cannot escape from a black hole, for any object-a particle, spacecraft, or wave-to escape, it would have to move past light. Nevertheless, light moves outward at the speed c. According to relativity, c is the highest attainable speed, so nothing can pass it. The black holes that Einstein envisioned, then, allow no escape whatsoever. An extension of this argument shows that when gravitation is this strong, nothing can even stay in the same place, but must move inward. Even the surface of a star must move inward, and must continue the collapse that created the strong gravitational force. What remains then is not a star, but a region of space from which emerges a tremendous gravitational force.
Einstein's theory of gravitation revolutionized 20th-century physics. Another important revolution that took place was quantum theory. Quantum theory states that physical interactions, or the exchange of energy, cannot be made arbitrarily small. There is a minimal interaction that comes in a packet called the quantum of an interaction. For electromagnetism the quantum is called the photon. Like the other interactions, gravitation also must be quantized. Physicists call a quantum of gravitational energy a graviton. In principle, gravitational waves arriving at the earth would consist of gravitons. In practice, gravitational waves would consist of apparently continuous streams of gravitons, and individual gravitons could not be detected.
Einstein's theory did not include quantum effects. For most of the 20th century, theoretical physicists have been unsuccessful in their attempts to formulate a theory that resembles Einstein's theory but also includes gravitons. Despite the lack of a complete quantum theory, making some partial predictions about quantized gravitation is possible. In the 1970s, British physicist Stephen Hawking showed that quantum mechanical processes in the strong gravitational pull just outside of black holes would create particles and quanta that move away from the black hole, thereby robbing it of energy.
Astronomy, is the study of the universe and the celestial bodies, gas, and dust within it. Astronomy includes observations and theories about the solar system, the stars, the galaxies, and the general structure of space. Astronomy also includes cosmology, the study of the universe and its past and future. People whom analysis astronomy is called astronomers, and they use a wide variety of methods to achieve of what in finality is obtainably resolved through their research. These methods usually involve ideas of physics, so most astronomers are also astrophysicists, and the term’s astronomer and astrophysicist are basically identical. Some areas of astronomy also use techniques of chemistry, geology, and biology.
Astronomy is the oldest science, dating back thousands of years to when primitive people noticed objects in the sky overhead and watched the way the objects moved. In ancient Egypt, he first appearance of certain stars each year marked the onset of the seasonal flood, an important event for agriculture. In 17th-century England, astronomy provided methods of keeping track of time that were especially useful for accurate navigation. Astronomy has a long tradition of practical results, such as our current understanding of the stars, day and night, the seasons, and the phases of the Moon. Much of today's research in astronomy does not address immediate practical problems. Instead, it involves basic research to satisfy our curiosity about the universe and the objects in it. One day such knowledge may be of practical use to humans.
Astronomers use tools such as telescopes, cameras, spectrographs, and computers to analyse the light that astronomical objects emit. Amateur astronomers observe the sky as a hobby, while professional astronomers are paid for their research and usually work for large institutions such as colleges, universities, observatories, and government research institutes. Amateur astronomers make valuable observations, but are often limited by lack of access to the powerful and expensive equipment of professional astronomers.
A wide range of astronomical objects is accessible to amateur astronomers. Many solar system objects-such as planets, moons, and comets - are bright enough to be visible through binoculars and small telescopes. Small telescopes are also sufficient to reveal some of the beautiful detail in nebulas-clouds of gas and dust in our galaxy. Many amateur astronomers observe and photograph these objects. The increasing availability of sophisticated electronic instruments and computers over the past few decades has made powerful equipment more affordable and allowed amateur astronomers to expand their observations too much fainter objects. Amateur astronomers sometimes share their observations by posting their photographs on the World Wide Web, a network of information based on connections between computers.
Amateurs often undertake projects that require numerous observations over days, weeks, months, or even years. By searching the sky over a long period of time, amateur astronomers may observe things in the sky that represent sudden change, such as new comets or novas (stars that brightens suddenly). This type of consistent observation is also useful for studying objects that change slowly over time, such as variable stars and double stars. Amateur astronomers observe meteor showers, sunspots, and groupings of planets and the Moon in the sky. They also participate in expeditions to places in which special astronomical events-such as solar eclipses and meteor showers-are most visible. Several organizations, such as the Astronomical League and the American Association of Variable Star Observers, provide meetings and publications through which amateur astronomers can communicate and share their observations.
Professional astronomers usually have access to powerful telescopes, detectors, and computers. Most work in astronomy includes three parts, or phases. Astronomers first observe astronomical objects by guiding telescopes and instruments to collect the appropriate information. Astronomers then analyse the images and data. After the analysis, they compare their results with existing theories to determine whether their observations match with what theories predict, or whether the theories can be improved. Some astronomers work solely on observation and analysis, and some work solely on developing new theories.
Astronomy is such a broad topic that astronomers specialize in one or more parts of the field. For example, the study of the solar system is a different area of specialization than the study of stars. Astronomers who study our galaxy, the Milky Way, often use techniques different from those used by astronomers who study distant galaxies. Many planetary astronomers, such as scientists who study Mars, may have geology backgrounds and not consider they astronomers at all. Solar astronomers use different telescopes than nighttime astronomers use, because the Sun is so bright. Theoretical astronomers may never use telescopes at all. Instead, these astronomers use existing data or sometimes only previous theoretical results to develop and test theories. An increasing field of astronomy is computational astronomy, in which astronomers use computers to simulate astronomical events. Examples of events for which simulations are useful include the formation of the earliest galaxies of the universe or the explosion of a star to make a supernova.
Astronomers learn about astronomical objects by observing the energy they emit. These objects emit energy in the form of electromagnetic radiation. This radiation travels throughout the universe in the form of waves and can range from gamma rays, which have extremely short wavelengths, to visible light, to radio waves, which are very long. The entire range of these different wavelengths makes up the electromagnetic spectrum.
Astronomers gather different wavelengths of electromagnetic radiation depending on the objects that are being studied. The techniques of astronomy are often very different for studying different wavelengths. Conventional telescopes work only for visible light and the parts of the spectrum near visible light, such as the shortest infrared wavelengths and the longest ultraviolet wavelengths. Earth’s atmosphere complicates studies by absorbing many wavelengths of the electromagnetic spectrum. Gamma-ray astronomy, X-ray astronomy, infrared astronomy, ultraviolet astronomy, radio astronomy, visible-light astronomy, cosmic-ray astronomy, gravitational-wave astronomy, and neutrino astronomy all use different instruments and techniques.
Observational astronomers use telescopes or other instruments to observe the heavens. The astronomers who do the most observing, however, probably spend more time using computers than they do using telescopes. A few nights of observing with a telescope often provide enough data to keep astronomers busy for months analysing the data.
Until the 20th century, all observational astronomers studied the visible light that astronomical objects emit. Such astronomers are called optical astronomers, because they observe the same part of the electromagnetic spectrum that the human eye sees. Optical astronomers use telescopes and imaging equipment to study light from objects. Professional astronomers today hardly ever look through telescopes. Instead, a telescope sends an object’s light to a photographic plate or to an electronic light-sensitive computer chip called a charge-coupled device, or CCD. CCDs are about fifty times more sensitive than film, so today's astronomers can record in a minute an image that would have taken about an hour to record on film.
Telescopes may use either lenses or mirrors to gather visible light, permitting direct observation or photographic recording of distant objects. Those that use lenses are called refracting telescopes, since they use the property of refraction, or bending, of light. The largest refracting telescope is the 40-in (1-m) telescope at the Yerkes Observatory in Williams Bay, Wisconsin, founded in the late 19th century. Lenses bend different colours of light by different amounts, so different colours focus differently. Images produced by large lenses can be tinged with colour, often limiting the observations to those made through filters. Filters limit the image to one colour of light, so the lens bends all of the light in the image the same amount and makes the image more accurate than an image that includes all colours of light. Also, because light must pass through lenses, lenses can only be supported at the very edges. Large, heavy lenses are so thick that all the large telescopes in current use are made with other techniques.
Reflecting telescopes, which use mirrors, are easier to make than refracting telescopes and reflect all colours of light equally. All the largest telescopes today are reflecting telescopes. The largest single telescopes are the Keck telescopes at Mauna Kea Observatory in Hawaii. The Keck telescope mirrors are 394 in (10.0 m) in diameter. Mauna Kea Observatory, at an altitude of 4,205 m (13,796 ft), is especially high. The air at the observatory is clear, so many major telescope projects are located there.
The Hubble Space Telescope (HST), a reflecting telescope that orbits Earth, has returned the clearest images of any optical telescope. The main mirror of the HST is only ninety-four in. (2.4 m.) across, far smaller than that of the largest ground-based reflecting telescopes. Turbulence in the atmosphere makes observing objects as clearly as the HST can see impossible for ground-based telescopes. HST images of visible light are about five times finer than any produced by ground-based telescopes. Giant telescopes on Earth, however, collect much more light than the HST can. Examples of such giant telescopes include the twin 32-ft (10-m) Keck telescopes in Hawaii and the four 26-ft (8-m) telescopes in the Very Large Telescope array in the Atacama Desert in northern Chile (the nearest city is Antofagasta, Chile). Often astronomers use space and ground-based telescopes in conjunction.
Astronomers usually share telescopes. Many institutions with large telescopes accept applications from any astronomer who wishes to use the instruments, though others have limited sets of eligible applicants. The institution then divides the available time between successful applicants and assigns each astronomer an observing period. Astronomers can collect data from telescopes remotely. Data from Earth-based telescopes can be sent electronically over computer networks. Data from space-based telescopes reach Earth through radio waves collected by antennas on the ground.
Gamma rays have the shortest wavelengths. Special telescopes in orbit around Earth, such as the National Aeronautics and Space Administration’s (NASA’s) Compton Gamma-Ray Observatory, gather gamma rays before Earth’s atmosphere absorbs them. X rays, the next shortest wavelengths, also must be observed from space. NASA’s Chandra x-ray Observatory (CXO) is a school-bus-sized spacecraft scheduled to begin studying X-rays from orbit in 1999. It is designed to make high-resolution images.
Ultraviolet light has wavelengths longer than X rays, but shorter than visible light. Ultraviolet telescopes are similar to visible-light telescopes in the way they gather light, but the atmosphere blocks most ultraviolet radiation. Most ultraviolet observations, therefore, must also take place in space. Most of the instruments on the Hubble Space Telescope (HST) are sensitive to ultraviolet radiation. Humans cannot see ultraviolet radiation, but astronomers can create visual images from ultraviolet light by assigning particular colours or shades to different intensities of radiation.
Infrared astronomers study parts of the infrared spectrum, which consists of electromagnetic waves with wavelengths ranging from just longer than visible light to 1,000 times longer than visible light. Earth’s atmosphere absorbs infrared radiation, so astronomers must collect infrared radiation from places where the atmosphere is very thin, or from above the atmosphere. Observatories for these wavelengths are located on certain high mountaintops or in space. Most infrared wavelengths can be observed only from space. Every warm object emits some infrared radiation. Infrared astronomy is useful because objects that are not hot enough to emit visible or ultraviolet radiation may still emit infrared radiation. Infrared radiation also passes through interstellar and intergalactic gas and dusts more easily than radiation with shorter wavelengths. Further, the brightest part of the spectrum from the farthest galaxies in the universe is shifted into the infrared. The Next Generation Space Telescope, which NASA plans to launch in 2006, will operate especially in the infrared.
Radio waves have the longest wavelengths. Radio astronomers use giant dish antennas to collect and focus signals in the radio part of the spectrum. These celestial radio signals, often from hot bodies in space or from objects with strong magnetic fields, come through Earth's atmosphere to the ground. Radio waves penetrate dust clouds, allowing astronomers to see into the centre of our galaxy and into the cocoons of dust that surround forming stars.
Sometimes astronomers study emissions from space that are not electromagnetic radiation. Some of the particles of interest to astronomers are neutrinos, cosmic rays, and gravitational waves. Neutrinos are tiny particles with no electric charge and very little or no mass. The Sun and supernovas emit neutrinos. Most neutrino telescopes consist of huge underground tanks of liquid. These tanks capture a few of the many neutrinos that strike them, while the vast majority of neutrinos pass right through the tanks.
Cosmic rays are electrically charged particles that come to Earth from outer space at almost the speed of light. They are made up of negatively charged particles called electrons and positively charged nuclei of atoms. Astronomers do not know where most cosmic rays come from, but they use cosmic-ray detectors to study the particles. Cosmic-ray detectors are usually grids of wires that produce an electrical signal when a cosmic ray passes close to them.
Gravitational waves are a predicted consequence of the general theory of relativity developed by German-born American physicist Albert Einstein. Set off up in the 1960s astronomers have been building detectors for gravitational waves. Older gravitational-wave detectors were huge instruments that surrounded a carefully measured and positioned massive object suspended from the top of the instrument. Lasers trained on the object were designed to measure the object’s movement, which theoretically would occur when a gravitational wave hit the object. At the end of the 20th century, these instruments had picked up no gravitational waves. Gravitational waves should be very weak, and the instruments were probably not yet sensitive enough to register them. In the 1970s and 1980s American physicists Joseph Taylor and Russell Hulse observed indirect evidence of gravitational waves by studying systems of double pulsars. A new generation of gravitational-wave detectors, developed in the 1990s, used interferometers to measure distortions of space that would be caused by passing gravitational waves.
Some objects emit radiation more strongly in one wavelength than in another, but a set of data across the entire spectrum of electromagnetic radiation is much more useful than observations in anyone wavelength. For example, the supernova remnant known as the Crab Nebula has been observed in every part of the spectrum, and astronomers have used all the discoveries together to make a complete picture of how the Crab Nebula is evolving.
Whether astronomers take data from a ground-based telescope or have data radioed to them from space, they must then analyse the data. Usually the data are handled with the aid of a computer, which can carry out various manipulations the astronomer requests. For example, some of the individual picture elements, or pixels, of a CCD may be more sensitive than others. Consequently, astronomers sometimes take images of blank sky to measure which pixels appear brighter. They can then take these variations into account when interpreting the actual celestial images. Astronomers may write their own computer programs to analyse data or, as is increasingly the case, use certain standard computer programs developed at national observatories or elsewhere.
Often an astronomer uses observations to test a specific theory. Sometimes, a new experimental capability allows astronomers to study a new part of the electromagnetic spectrum or to see objects in greater detail or through special filters. If the observations do not verify the predictions of a theory, the theory must be discarded or, if possible, modified.
Up to about 3,000 stars are visible at a time from Earth with the unaided eye, far away from city lights, on a clear night. A view at night may also show several planets and perhaps a comet or a meteor shower. Increasingly, human-made light pollution is making the sky less dark, limiting the number of visible astronomical objects. During the daytime the Sun shines brightly. The Moon and bright planets are sometimes visible early or late in the day but are rarely seen at midday.
Earth moves in two basic ways: It turns in place, and it revolves around the Sun. Earth turns around its axis, an imaginary line that runs down its centre through its North and South poles. The Moon also revolves around Earth. All of these motions produce day and night, the seasons, the phases of the Moon, and solar and lunar eclipses.
Earth is about 12,000 km. (about 7,000 mi.) in diameter. As it revolves, or moves in a circle, around the Sun, Earth spins on its axis. This spinning movement is called rotation. Earth’s axis is tilted 23.5° with respect to the plane of its orbit. Each time Earth rotates on its axis, its corrective velocity to enable it of travelling, or free falling through into a new day, in other words, its rotational inertia or axial momentum carries it through one day, a cycle of light and dark. Humans artificially divide the day into 24 hours and then divide the hours into 60 minutes and the minutes into 60 seconds.
Earth revolves around the Sun once every year, or 365.25 days (most people use a 365-day calendar and take care of the extra 0.25 day by adding a day to the calendar every four years, creating a leap year). The orbit of Earth is almost, but not quite, a circle, so Earth is sometimes a little closer to the Sun than at other times. If Earth were upright as it revolved around the Sun, each point on Earth would have exactly twelve hours of light and twelve hours of dark each day. Because Earth is tilted, however, the northern hemisphere sometimes points toward the Sun and sometimes points away from the Sun. This tilt is responsible for the seasons. When the northern hemisphere points toward the Sun, the northernmost regions of Earth see the Sun 24 hours a day. The whole northern hemisphere gets more sunlight and gets it at a more direct angle than the southern hemisphere does during this period, which lasts for half of the year. The second half of this period, when the northern hemisphere points most directly at the Sun, is the northern hemisphere's summer, which corresponds to winter in the southern hemisphere. During the other half of the year, the southern hemisphere points more directly toward the Sun, so it is spring and summer in the southern hemisphere and fall and winters in the northern hemisphere.
One revolution of the Moon around Earth takes a little more than twenty-seven days seven hours. The Moon rotates on its axis in this same period of time, so the same face of the Moon is always presented to Earth. Over a period a little longer than twenty-nine days twelve hours, the Moon goes through a series of phases, in which the amount of the lighted half of the Moon we see from Earth changes. These phases are caused by the changing angle of sunlight hitting the Moon. (The period of phases is longer than the period of revolution of the Moon, because the motion of Earth around the Sun changes the angle at which the Sun’s light hits the Moon from night to night.)
The Moon’s orbit around Earth is tilted five from the plane of Earth’s orbit. Because of this tilt, when the Moon is at the point in its orbit when it is between Earth and the Sun, the Moon is usually a little above or below the Sun. At that time, the Sun lights the side of the Moon facing away from Earth, and the side of the Moon facing toward Earth is dark. This point in the Moon’s orbit corresponds to a phase of the Moon called the new moon. A quarter moon occurs when the Moon is at right angles to the line formed by the Sun and Earth. The Sun lights the side of the Moon closest to it, and half of that side is visible from Earth, forming a bright half-circle. When the Moon is on the opposite side of Earth from the Sun, the face of the Moon visible from Earth is lit, showing the full moon in the sky
Because of the tilt of the Moon's orbit, the Moon usually passes above or below the Sun at new moon and above or below Earth's shadow at full moon. Sometimes, though, the full moon or new moon crosses the plane of Earth's orbit. By a coincidence of nature, even though the Moon is about 400 times smaller than the Sun, it is also about 400 times closer to Earth than the Sun is, so the Moon and Sun look almost the same size from Earth. If the Moon lines up with the Sun and Earth at new moon (when the Moon is between Earth and the Sun), it blocks the Sun’s light from Earth, creating a solar eclipse. If the Moon lines up with Earth and the Sun at the full moon (when Earth is between the Moon and the Sun), Earth’s shadow covers the Moon, making a lunar eclipse.
A total solar eclipse is visible from only a small region of Earth. During a solar eclipse, the complete shadow of the Moon that falls on Earth is only about 160 km. (about 100 mi.) wide. As Earth, the Sun, and the Moon move, however, the Moon’s shadow sweeps out a path up to 16,000 km. (10,000 mi.) long. The total eclipse can only be seen from within this path. A total solar eclipse occurs about every eighteen months. Off to the sides of the path of a total eclipse, a partial eclipse, in which the Sun is only partly covered, is visible. Partial eclipses are much less dramatic than total eclipses. The Moon’s orbit around Earth is elliptical, or egg-shaped. The distance between Earth and the Moon varies slightly as the Moon orbits Earth. When the Moon is farther from Earth than usual, it appears smaller and may not cover the entire Sun during an eclipse. A ring, or annulus, of sunlight remains assimilated through visibility. Making an annular eclipse. An annular solar eclipse also occurs about every eighteen months. Additional partial solar eclipses are also visible from Earth in between.
At a lunar eclipse, the Moon is existent in Earth's shadow. When the Moon is completely in the shadow, the total lunar eclipse is visible from everywhere on the half of Earth from which the Moon is visible at that time. As a result, more people see total lunar eclipses than see total solar eclipses.
In an open place on a clear dark night, streaks of light may appear in a random part of the sky about once every ten minutes. These streaks are meteors-bits of rock-turning up in Earth's atmosphere. The bits of rock are called meteoroids, and when these bits survive Earth’s atmosphere intact and land on Earth, they are known as meteorites.
Every month or so, Earth passes through the orbit of a comet. Dust from the comet remains in the comet's orbit. When Earth passes through the band of dust, the dust and bits of rock burn up in the atmosphere, creating a meteor shower. Many more meteors are visible during a meteor shower than on an ordinary night. The most observed meteor shower is the Perseid shower, which occurs each year on August 11th or 12th.
Humans have picked out landmarks in the sky and mapped the heavens for thousands of years. Maps of the sky helped to potentially lost craft in as much as sailors have navigated using the celestially fixed stars to find refuge away from being lost. Now astronomers methodically map the sky to produce a universal format for the addresses of stars, galaxies, and other objects of interest.
Some of the stars in the sky are brighter and more noticeable than others are, and some of these bright stars appear to the eye to be grouped together. Ancient civilizations imagined that groups of stars represented figures in the sky. The oldest known representations of these groups of stars, called constellations, are from ancient Sumer (now Iraq) from about 4000 Bc. The constellations recorded by ancient Greeks and Chinese resemble the Sumerian constellations. The northern hemisphere constellations that astronomers recognize today are based on the Greek constellations. Explorers and astronomers developed and recorded the official constellations of the southern hemisphere in the 16th and 17th centuries. The International Astronomical Union (IAU) officially recognizes eighty-eight constellations. The IAU defined the boundaries of each constellation, so the eighty-eight constellations divide the sky without overlapping.
A familiar group of stars in the northern hemisphere is called the Big Dipper. The Big Dipper is part of an official constellation-Ursa Major, or the Great Bear. Groups of stars that are not official constellations, such as the Big Dipper, are called asterisms. While the stars in the Big Dipper appear in approximately the same part of the sky, they vary greatly in their distance from Earth. This is true for the stars in all constellations or asterisms-the stars accumulating of the group do not really occur close to each other in space, they merely appear together as seen from Earth. The patterns of the constellations are figments of humans’ imagination, and different artists may connect the stars of a constellation in different ways, even when illustrating the same myth.
Astronomers use coordinate systems to label the positions of objects in the sky, just as geographers use longitude and latitude to label the positions of objects on Earth. Astronomers use several different coordinate systems. The two most widely used are the altazimuth system and the equatorial system. The altazimuth system gives an object’s coordinates with respect to the sky visible above the observer. The equatorial coordinate system designates an object’s location with respect to Earth’s entire night sky, or the celestial sphere.
One of the ways astronomers give the position of a celestial object is by specifying its altitude and its azimuth. This coordinate system is called the altazimuth system. The altitude of an object is equal to its angle, in degrees, above the horizon. An object at the horizon would have an altitude of zero, and an object directly overhead would have an altitude of ninety. The azimuth of an object is equal to its angle in the horizontal direction, with north at zero, east at ninety, south at 180°, and west at 270°. For example, if an astronomer were looking for an object at twenty-three altitude and eighty-seven azimuth, the astronomer would know to look low in the sky and almost directly east.
As Earth rotates, astronomical objects appear to rise and set, so their altitudes and azimuths are constantly changing. An object’s altitude and azimuth also vary according to an observer’s location on Earth. Therefore, astronomers almost never use altazimuth coordinates to record an object’s position. Instead, astronomers with altazimuth telescopes translate coordinates from equatorial coordinates to find an object. Telescopes that use an altazimuth mounting system may be simple to set up, but they require many calculated movements to keep them pointed at an object as it moves across the sky. These telescopes fell out of use with the development of the equatorial coordinate and mounting system in the early 1800s. However, computers have made the return to popularity possible for altazimuth systems. Altazimuth mounting systems are simple and inexpensive, and-with computers to do the required calculations and control the motor that moves the telescope-they are practical.
The equatorial coordinate system is a coordinate system fixed on the sky. In this system, a star keeps the same coordinates no matter what the time is or where the observer is located. The equatorial coordinate system is based on the celestial sphere. The celestial sphere is a giant imaginary globe surrounding Earth. This sphere has north and south celestial pole directly above Earth’s North and South poles. It has a celestial equator, directly above Earth’s equator. Another important part of the celestial sphere is the line that marks the movement of the Sun with respect to the stars throughout the year. This path is called the ecliptic. Because Earth is tilted with respect to its orbit around the Sun, the ecliptic is not the same as the celestial equator. The ecliptic is tilted 23.5° to the celestial equator and crosses the celestial equator at two points on opposite sides of the celestial sphere. The crossing points are called the vernal (or spring) equinox and the autumnal equinox. The vernal equinox and autumnal equinox mark the beginning of spring and fall, respectively. The points at which the ecliptic and celestial equator are farthest apart are called the summer solstice and the winter solstice, which mark the beginning of summer and winter, respectively.
As Earth rotates on its axis each day, the stars and other distant astronomical objects appear to rise in the eastern part of the sky and set in the west. They seem to travel in circles around Earth’s North or South poles. In the equatorial coordinate system, the celestial sphere turns with the stars (but this movement is really caused by the rotation of Earth). The celestial sphere makes one complete rotation every twenty-three hours fifty-six minutes, which is four unexpected moments than a day measured by the movement of the Sun. A complete rotation of the celestial sphere is called a sidereal day. Because the sidereal day is shorter than a solar day, the stars that an observer sees from any location on Earth change slightly from night to night. The difference between a sidereal day and a solar day occurs because of Earth’s motion around the Sun.
The equivalent of longitude on the celestial sphere is called right ascension and the equivalent of latitude is declination. Specifying the right ascension of a star is equivalent to measuring the east-west distance from a line called the prime meridian that runs through Greenwich, England, for a place on Earth. Right ascension starts at the vernal equinox. Longitude on Earth is given in degrees, but right ascension is given in units of time-hours, minutes, and seconds. This is because the celestial equator is divided into 24 equal parts-each called an hour of right ascension instead of fifteen. Each hour is made up of 60 minutes, each of which is equal to 60 seconds. Measuring right ascension in units of time makes determine when will be the best time for observing an object easier for astronomers. A particular line of right ascension will be at its highest point in the sky above a particular place on Earth four minutes earlier each day, so keeping track of the movement of the celestial sphere with an ordinary clock would be complicated. Astronomers have special clocks that keep sidereal time (24 sidereal hours are equal to twenty-three hours fifty-six minutes of familiar solar time). Astronomers compare the current sidereal time with the right ascension of the object they wish to view. The object will be highest in the sky when the sidereal time equals the right ascension of the object.
The direction perpendicular to right ascension-and the equivalent to latitude on Earth-is declination. Declination is measured in degrees. These degrees are divided into arcminutes and arcseconds. One arcminute is equal to 1/60 of a degree, and one arcsecond is equal to 1/60 of an arcminute, or 1/360 of a degree. The celestial equator is at declination zero, the north celestial pole is at declination ninety, and the south celestial pole has a declination of -90°. Each star has a right ascension and a declination that mark its position in the sky. The brightest star, Sirius, for example, has right ascension six hours forty-five minutes (abbreviated as 6h. 45m.) and declination-16 degrees forty-three arcminutes
Stars are so far away from Earth that the main star motion we see results from Earth’s rotation. Stars do move in space, however, and these proper motions slightly change the coordinates of the nearest stars over time. The effects of the Sun and the Moon on Earth also cause slight changes in Earth’s axis of rotation. These changes, called precession, cause a slow drift in right ascension and declination. To account for precession, astronomers redefine the celestial coordinates every fifty years or so.
Solar systems, both our own and those located around other stars, are a major area of research for astronomers. A solar system consists of a central star orbited by planets or smaller rocky bodies. The gravitational force of the star holds the system together. In our solar system, the central star is the Sun. It holds all the planets, including Earth, in their orbits and provides light and energy necessary for life. Our solar system is just one of many. Astronomers are just beginning to be able to study other solar systems.
Our solar system contains the Sun, nine planets (of which Earth is third from the Sun), and the planets’ satellites. It also contains asteroids, comets, and interplanetary dust and gases.
Until the end of the 18th century, humans knew of five planets-Mercury, Venus, Mars, Jupiter, and Saturn-in addition to Earth. When viewed without a telescope, planets appear to be dots of light in the sky. They shine steadily, while stars seem to twinkle. Twinkling results from turbulence in Earth's atmosphere. Stars are so far away that they appear as tiny points of light. A moment of turbulence can change that light for a fraction of a second. Even though they look the same size as stars to unaided human eyes, planets are close enough that they take up more space in the sky than stars do. The disks of planets are big enough to average out variations in light caused by turbulence and therefore do not twinkle.
Between 1781 and 1930, astronomers found three more planets-Uranus, Neptune, and Pluto. This brought the total number of planets in our solar system to nine. In order of increasing distance from the Sun, the planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
Astronomers call the inner planets-Mercury, Venus, Earth, and Mars-the terrestrial planets. Terrestrial (from the Latin word terra, meaning ‘Earth’) planets are Earthlike in that they have solid, rocky surfaces. The next group of planets-Jupiter, Saturn, Uranus, and Neptune-is called the Jovian planets, or the giant planets. The word Jovian has the same Latin root as the word Jupiter. Astronomers call these planets the Jovian planets because they resemble Jupiter in that they are giant, massive planets made almost entirely of gas. The mass of Jupiter, for example, is 318 times the mass of Earth. The Jovian planets have no solid surfaces, although they probably have rocky cores several times more massive than Earth. Rings of chunks of ice and rock surround each of the Jovian planets. The rings around Saturn are the most familiar.
Pluto, the outermost planet, is tiny, with a mass about one five-hundredth the mass of Earth. Pluto seems out of place, with its tiny, solid body out beyond the giant planets. Many astronomers believe that Pluto is really just the largest, or one of the largest, of a group of icy objects in the outer solar system. These objects orbit in a part of the solar system called the Kuiper Belt. Even if astronomers decide that Pluto belongs to the Kuiper Belt objects, it will probably still be called a planet for historical reasons.
Most of the planets have moons, or satellites. Earth's Moon has a diameter about one-fourth the diameter of Earth. Mars has two tiny chunks of rock, Phobos and Deimos, each only about 10 km (about 6 mi) across. Jupiter has at least seventeen satellites. The largest four, known as the Galilean satellites, are Io, Europa, Ganymede, and Callisto. Ganymede is even larger than the planet Mercury. Saturn has at least eighteen satellites. Saturn’s largest moon, Titan, is also larger than the planet Mercury and is enshrouded by a thick, opaque, smoggy atmosphere. Uranus has at least seventeen moons, and Neptune has at least eight moons. Pluto had one moon, called Charon. Charon is more than half as big as Pluto.
Comets and asteroids are rocky and icy bodies that are smaller than planets. The distinction between comets, asteroids, and other small bodies in the solar system is a little fuzzy, but generally a comet is icier than an asteroid and has a more elongated orbit. The orbit of a comet takes it close to the Sun, then back into the outer solar system. When comets near the Sun, some of their ice turns from solid material into gas, releasing some of their dust. Comets have long tails of glowing gas and dust when they are near the Sun. Asteroids are rockier bodies and usually have orbits that keep them at always about the same distance from the Sun.
Both comets and asteroids have their origins in the early solar system. While the solar system was forming, many small, rocky objects called planetesimals condensed from the gas and dust of the early solar system. Millions of planetesimals remain in orbit around the Sun. A large spherical cloud of such objects out beyond Pluto forms the Oort cloud. The objects in the Oort cloud are considered comets. When our solar system passes close to another star or drifts closer than usual to the centre of our galaxy, the change in gravitational pull may disturb the orbit of one of the icy comets in the Oort cloud. As this comet falls toward the Sun, the ice turns into vapour, freeing dust from the object. The gas and dust form the tail or tails of the comet. The gravitational pull of large planets such as Jupiter or Saturn may swerve the comet into an orbit closer to the Sun. The time needed for a comet to make a complete orbit around the Sun is called the comet’s period. Astronomers believe that comets with periods longer than about 200 years come from the Oort Cloud. Short-period comets, those with periods less than about 200 years, probably come from the Kuiper Belt, a ring of planetesimals beyond Neptune. The material in comets is probably from the very early solar system, so astronomers study comets to find out more about our solar system’s formation.
When the solar system was forming, some of the planetesimals came together more toward the centre of the solar system. Gravitational forces from the giant planet Jupiter prevented these planetesimals from forming full-fledged planets. Instead, the planetesimals broke up to create thousands of minor planets, or asteroids, that orbit the Sun. Most of them are in the asteroid belt, between the orbits of Mars and Jupiter, but thousands are in orbits that come closer to Earth or even cross Earth's orbit. Scientists are increasingly aware of potential catastrophes if any of the largest of these asteroids hits Earth. Perhaps 2,000 asteroids larger than 1 km. (0.6 mi.) in diameter are potential hazards.
The Sun is the nearest star to Earth and is the centre of the solar system. It is only eight light-minutes away from Earth, meaning light takes only eight minutes to travel from the Sun to Earth. The next nearest star is four light-years away, so light from this star, Proxima Centauri (part of the triple star Alpha Centauri), takes four years to reach Earth. The Sun's closeness means that the light and other energy we get from the Sun dominate Earth’s environment and life. The Sun also provides a way for astronomers to study stars. They can see details and layers of the Sun that are impossible to see on more distant stars. In addition, the Sun provides a laboratory for studying hot gases held in place by magnetic fields. Scientists would like to create similar conditions (hot gases contained by magnetic fields) on Earth. Creating such environments could be useful for studying basic physics.
The Sun produces its energy by fusing hydrogen into helium in a process called nuclear fusion. In nuclear fusion, two atoms merge to form a heavier atom and release energy. The Sun and stars of similar mass start off with enough hydrogen to shine for about ten billion years. The Sun is less than halfway through its lifetime.
Although most telescopes are used mainly to collect the light of faint objects so that they can be studied, telescopes for planetary and other solar system studies are also used to magnify images. Astronomers use some of the observing time of several important telescopes for planetary studies. Overall, planetary astronomers must apply and compete for observing time on telescopes with astronomers seeking to study other objects. Some planetary objects can be studied as they pass in front of, or occult, distant stars. The atmosphere of Neptune's moon Triton and the shapes of asteroids can be investigated in this way, for example. The fields of radio and infrared astronomy are useful for measuring the temperatures of planets and satellites. Ultraviolet astronomy can help astronomers study the magnetic fields of planets.
During the space age, scientists have developed telescopes and other devices, such as instruments to measure magnetic fields or space dust, that can leave Earth's surface and travel close to other objects in the solar system. Robotic spacecraft have visited all of the planets in the solar system except Pluto. Some missions have targeted specific planets and spent much time studying a single planet, and some spacecraft have flown past a number of planets.
Astronomers use different telescopes to study the Sun than they use for nighttime studies because of the extreme brightness of the Sun. Telescopes in space, such as the Solar and Heliospheric Observatory (SOHO) and the Transition Region and Coronal Explorer (TRACE), are able to study the Sun in regions of the spectrum other than visible light. X-rays, ultraviolet, and radio waves from the Sun are especially interesting to astronomers. Studies in various parts of the spectrum give insight into giant flows of gas in the Sun, into how the Sun's energy leaves the Sun to travel to Earth, and into what the interior of the Sun is like. Astronomers also study solar-terrestrial relations-the relation of activity on the Sun with magnetic storms and other effects on Earth. Some of these storms and effects can affect radio reception, cause electrical blackouts, or damage satellites in orbit.
Our solar system began forming about five billion years ago, when a cloud of gas and dust between the stars in our Milky Way Galaxy began contracting. A nearby supernova-an exploding star-may have started the contraction, but most astronomers believe a random change in density in the cloud caused the contraction. Once the cloud-known as the solar nebula-began to contract, the contraction occurred faster and faster. The gravitational energy caused by this contraction heated the solar nebula. As the cloud became smaller, it began to spin faster, much as a spinning skater will spin faster by pulling in his or her arms. This spin kept the nebula from forming a sphere; instead, it settled into a disk of gas and dust.
In this disk, small regions of gas and dust began to draw closer and stick together. The objects that resulted, which were usually less than 500 km (300 mi) across, are the planetesimals. Eventually, some planetesimals stuck together and grew to form the planets. Scientists have made computer models of how they believe the early solar system behaved. The models show that for a solar system to produce one or two huge planets like Jupiter and several other, much smaller planets is usual.
The largest region of gas and dust wound up in the centre of the nebula and formed the protosun (proto is Greek for ‘before’ and is used to distinguish between an object and its forerunner). The increasing temperature and pressure in the middle of the protosun vaporized the dust and eventually allowed nuclear fusion to begin, marking the formation of the Sun. The young Sun gave off a strong solar wind that drove off most of the lighter elements, such as hydrogen and helium, from the inner planets. The inner planets then solidified and formed rocky surfaces. The solar wind lost strength. Jupiter’s gravitational pull was strong enough to keep its shroud of hydrogen and helium gas. Saturn, Uranus, and Neptune also kept their layers of light gases.
The theory of solar system formation described above accounts for the appearance of the solar system as we know it. Examples of this appearance include the fact that the planets all orbit the Sun in the same direction and that almost all the planets rotate on their axes in the same direction. The recent discoveries of distant solar systems with different properties could lead to modifications in the theory, however
Studies in the visible, the infrared, and the shortest radio wavelengths have revealed disks around several young stars in our galaxy. One such object, Beta Pictoris (about sixty-two light-years from Earth), has revealed a warp in the disk that could be a sign of planets in orbit. Astronomers are hopeful that, in the cases of these young stars, they are studying the early stages of solar system formation.
Although astronomers have long assumed that many other stars have planets, they have been unable to detect these other solar systems until recently. Planets orbiting around stars other than the Sun are called extra solar planets. Planets are small and dim compared with stars, so they are lost in the glare of their parent stars and are invisible to direct observation with telescopes.
Astronomers have tried to detect other solar systems by searching for the way a planet affects the movement of its parent star. The gravitational attraction between a planet and its star pulls the star slightly toward the planet, so the star wobbles slightly as the planet orbits it. Throughout the mind and late 1900s, several observatories tried to detect wobbles in the nearest stars by watching the stars’ movement across the sky. Wobbles were reported in several stars, but later observations showed that the results were false.
In the early 1990s, studies of a pulsar revealed at least two planets orbiting it. Pulsars are compact stars that give off pulses of radio waves at very regular intervals. The pulsar, designated PSR 1257+12, is about 1,000 light-years from Earth. This pulsar's pulses sometimes came a little early and sometimes a little late in a periodic pattern, revealing that an unseen object was pulling the pulsar toward and away from Earth. The environment of a pulsar, which emits X rays and other strong radiation that would be harmful to life on Earth, is so extreme that these objects would have little resemblance to planets in our solar system.
The wobbling of a star changes the star’s light that reaches Earth. When the star moves away from Earth, even slightly, each wave of light must travel farther to Earth than the wave before it. This increases the distance between waves (called the wavelength) as the waves reach Earth. When a star’s planet pulls the star closer to Earth, each successive wavefront has less distance to travel to reach Earth. This shortens the wavelength of the light that reaches Earth. This effect is called the Doppler effect. No star moves fast enough for the change in wavelength to result in a noticeable change in colour, which depends on wavelength, but the changes in wavelength can be measured with precise instruments. Because the planet’s effect on the star is very small, astronomers must analyse the starlight carefully to detect a shift in wavelength. They do this by first using a technique called spectroscopy to separate the white starlight into its component colours, as water vapour does to sunlight in a rainbow. Stars emit light in a continuous range. The range of wavelengths a star emits is called the star’s spectrum. This spectrum had dark lines, called absorption lines, at wavelengths at which atoms in the outermost layers of the star absorb light.
Astronomers know what the exact wavelength of each absorption line is for a star that is not moving. By seeing how far the movement of a star shifts the absorption lines in its spectrum, astronomers can calculate how fast the star is moving. If the motion fits the model of the effect of a planet, astronomers can calculate the mass of the planet and how close it is to the star. These calculations can only provide the lower limit to the planet’s mass, because telling at what angle the planet orbits. The star is impossible for astronomers. Astronomers need to know the angle at which the planet orbits the star to calculate the planet’s mass accurately. Because of this uncertainty, some of the giant extra solar planets may be a type of failed star called a brown dwarf instead of planets. Most astronomers believe that many of the suspected planets are true planets.
Between 1995 and 1999 astronomers discovered more than a dozen extra solar planets. Astronomers now know of far more planets outside our solar system than inside our solar system. Most of these planets, surprisingly, are more massive than Jupiter and are orbiting so close to their parent stars that some of them have ‘years’ (the time it takes to orbit the parent star once) as long as only a few days on Earth. These solar systems are so different from our solar system that astronomers are still trying to reconcile them with the current theory of solar system formation. Some astronomers suggest that the giant extra solar planets formed much farther away from their stars and were later thrown into the inner solar systems by some gravitational interaction.
Stars are an important topic of astronomical research. Stars are balls of gas that shine or used to shine because of nuclear fusion in their cores. The most familiar star is the Sun. The nuclear fusion in stars produces a force that pushes the material in a star outward. However, the gravitational attraction of the star’s material for itself pulls the material inward. A star can remain stable as long as the outward pressure and gravitational force balance. The properties of a star depend on its mass, its temperature, and its stage in evolution.
Astronomers study stars by measuring their brightness or, with more difficulty, their distances from Earth. They measure the ‘colour’ of a star-the differences in the star’s brightness from one part of the spectrum to another-to determine its temperature. They also study the spectrum of a star’s light to determine not only the temperature, but also the chemical makeup of the star’s outer layers.
Many different types of stars exist. Some types of stars are really just different stages of a star’s evolution. Some types are different because the stars formed with much more or much less mass than other stars, or because they formed close to other stars. The Sun is a type of star known as a main-sequence star. Eventually, main-sequence stars such as the Sun swell into giant stars and then evolve into tiny, dense, white dwarf stars. Main-sequence stars and giants have a role in the behaviour of most variable stars and novas. A star much more massive than the Sun will become a supergiant star, then explode as a supernova. A supernova may leave behind a neutron star or a black hole.
In about 1910 Danish astronomer Ejnar Hertzsprung and American astronomer Henry Norris Russell independently worked out a way to graph basic properties of stars. On the horizontal axis of their graphs, they plotted the temperatures of stars. On the vertical axis, they plotted the brightness of stars in a way that allowed the stars to be compared. (One plotted the absolute brightness, or absolute magnitude, of a star, a measurement of brightness that takes into account the distance of the star from Earth. The other plotted stars in a nearby galaxy, all about the same distance from Earth.)
On an H-R diagram, the brightest stars are at the top and the hottest stars are at the left. Hertzsprung and Russell found that most stars fell on a diagonal line across the H-R diagram from upper left lower to right. This line is called the main sequence. The diagonal line of main-sequence stars indicates that temperature and brightness of these stars are directly related. The hotter a main-sequence stars is, the brighter it is. The Sun is a main-sequence star, located in about the middle of the graph. More faint, cool stars exist than hot, bright ones, so the Sun is brighter and hotter than most of the stars in the universe.
At the upper right of the H-R diagram, above the main sequence, stars are brighter than main-sequence stars of the same colour. The only way stars of a certain colour can be brighter than other stars of the same colour is if the brighter stars are also bigger. Bigger stars are not necessarily more massive, but they do have larger diameters. Stars that fall in the upper right of the H-R diagram are known as giant stars or, for even brighter stars, supergiant stars. Supergiant stars have both larger diameters and larger masses than giant stars.
Giant and supergiant stars represent stages in the lives of stars after they have burned most of their internal hydrogen fuel. Stars swell as they move off the main sequence, becoming giants and—for more massive stars-supergiants.
A few stars fall in the lower left portion of the H-R diagram, below the main sequence. Just as giant stars are larger and brighter than main-sequences stars, these stars are smaller and dimmer. These smaller, dimmer stars are hot enough to be white or blue-white in colour and are known as white dwarfs.
White dwarf stars are only about the size of Earth. They represent stars with about the mass of the Sun that have burned as much hydrogen as they can. The gravitational force of a white dwarf’s mass is pulling the star inward, but electrons in the star resist being pushed together. The gravitational force is able to pull the star into a much denser form than it was in when the star was burning hydrogen. The final stage of life for all stars like the Sun is the white dwarf stage.
Many stars vary in brightness over time. These variable stars come in a variety of types. One important type is called a Cepheid variable, named after the star delta Cepheid, which is a prime example of a Cepheid variable. These stars vary in brightness as they swell and contract over a period of weeks or months. Their average brightness depends on how long the period of variation takes. Thus astronomers can determine how bright the star is merely by measuring the length of the period. By comparing how intrinsically bright these variable stars are with how bright they look from Earth, astronomers can calculate how far away these stars are from Earth. Since they are giant stars and are very bright, Cepheid variables in other galaxies are visible from Earth. Studies of Cepheid variables tell astronomers how far away these galaxies are and are very useful for determining the distance scale of the universe. The Hubble Space Telescope (HST) can determine the periods of Cepheid stars in galaxies farther away than ground-based telescopes can see. Astronomers are developing a more accurate idea of the distance scale of the universe with HST data.
Cepheid variables are only one type of variable star. Stars called long-period variables vary in brightness as they contract and expand, but these stars are not as regular as Cepheid variables. Mira, a star in the constellation Cetus (the whale), is a prime example of a long-period variable star. Variable stars called eclipsing binary stars are really pairs of stars. Their brightness varies because one member of the pair appears to pass in front of the other, as seen from Earth. A type of variable star called R Coronae Borealis stars varies because they occasionally give off clouds of carbon dust that dim these stars.
Sometimes stars brighten drastically, becoming as much as 100 times brighter than they were. These stars are called novas (Latin for ‘new stars’). They are not really new, just much brighter than they were earlier. A nova is a binary, or double, star in which one member is a white dwarf and the other is a giant or supergiant. Matter from the large star falls onto the small star. After a thick layer of the large star’s atmosphere has collected on the white dwarf, the layer burns off in a nuclear fusion reaction. The fusion produces a huge amount of energy, which, from Earth, appears as the brightening of the nova. The nova gradually returns to its original state, and material from the large star again begins to collect on the white dwarf.
Sometimes stars brighten many times more drastically than novas do. A star that had been too dim to see can become one of the brightest stars in the sky. These stars are called supernovas. Sometimes supernovas that occur in other galaxies are so bright that, from Earth, they appear as bright as their host galaxy.
There are two types of supernovas. One type is an extreme case of a nova, in which matter falls from a giant or supergiant companion onto a white dwarf. In the case of a supernova, the white dwarf gains so much fuel from its companion that the star increases in mass until strong gravitational forces cause it to become unstable. The star collapses and the core explodes, vaporizing a lot of the white dwarves and producing an immense amount of light. Only bits of the white dwarf remain after this type of supernova occurs.
The other type of supernova occurs when a supergiant star uses up all its nuclear fuel in nuclear fusion reactions. The star uses up its hydrogen fuel, but the core is hot enough that it provides the initial energy necessary for the star to begin ‘burning’ helium, then carbon, and then heavier elements through nuclear fusion. The process stops when the core is mostly iron, which is too heavy for the star to ‘burn’ in a way that gives off energy. With no such fuel left, the inward gravitational attraction of the star’s material for itself has no outward balancing force, and the core collapses. As it collapses, the core releases a shock wave that tears apart the star’s atmosphere. The core continues collapsing until it forms either a neutron star or a black hole, depending on its mass
Only a handfuls of supernovas are known in our galaxy. The last Milky Way supernova seen from Earth was observed in 1604. In 1987 astronomers observed a supernova in the Large Magellanic Cloud, one of the Milky Way’s satellite galaxies. This supernova became bright enough to be visible to the unaided eye and is still under careful study from telescopes on Earth and from the Hubble Space Telescope. A supernova in the process of exploding emits radiation in the X-ray range and ultraviolet and radio radiation studies in this part of the spectrum are especially useful for astronomers studying supernova remnants.
Neutron stars are the collapsed cores sometimes left behind by supernova explosions. Pulsars are a special type of neutron star. Pulsars and neutron stars form when the remnant of a star left after a supernova explosion collapses until it is about 10 km. (about 6 mi.) in radius. At that point, the neutrons-electrically neutral atomic particles-of the star resists being pressed together further. When the force produced by the neutrons, balances, the gravitational force, the core stops collapsing. At that point, the star is so dense that a teaspoonful has the mass of a billion metric tons.
Neutron stars become pulsars when the magnetic field of a neutron star directs a beam of radio waves out into space. The star is so small that it rotates from one to a few hundred times per second. As the star rotates, the beam of radio waves sweeps out a path in space. If Earth is in the path of the beam, radio astronomers see the rotating beam as periodic pulses of radio waves. This pulsing is the reason these stars are called pulsars.
Some neutron stars are in binary systems with an ordinary star neighbour. The gravitational pull of a neutron star pulls material off its neighbour. The rotation of the neutron star heats the material, causing it to emit X-rays. The neutron star’s magnetic field directs the X-rays into a beam that sweeps into space and may be detected from Earth. Astronomers call these stars X-ray pulsars.
Gamma-ray spacecraft detect bursts of gamma rays about once a day. The bursts come from sources in distant galaxies, so they must be extremely powerful for us to be able to detect them. A leading model used to explain the bursts are the merger of two neutron stars in a distant galaxy with a resulting hot fireball. A few such explosions have been seen and studied with the Hubble and Keck telescopes.
Black holes are objects that are so massive and dense that their immense gravitational pull does not even let light escape. If the core left over after a supernova explosion has a mass of more than about fives times that of the Sun, the force holding up the neutrons in the core is not large enough to balance the inward gravitational force. No outward force is large enough to resist the gravitational force. The core of the star continues to collapse. When the core's mass is sufficiently concentrated, the gravitational force of the core is so strong that nothing, not even light, can escape it. The gravitational force is so strong that classical physics no longer applies, and astronomers use Einstein’s general theory of relativity to explain the behaviour of light and matter under such strong gravitational forces. According to general relativity, space around the core becomes so warped that nothing can escape, creating a black hole. A star with a mass ten times the mass of the Sun would become a black hole if it were compressed to 90 km. (60 mi.) or less in diameter.
Astronomers have various ways of detecting black holes. When a black hole is in a binary system, matter from the companion star spirals into the black hole, forming a disk of gas around it. The disk becomes so hot that it gives off X rays that astronomers can detect from Earth. Astronomers use X-ray telescopes in space to find X-ray sources, and then they look for signs that an unseen object of more than about five times the mass of the Sun is causing gravitational tugs on a visible object. By 1999 astronomers had found about a dozen potential black holes.
The basic method that astronomers use to find the distance of a star from Earth uses parallax. Parallax is the change in apparent position of a distant object when viewed from different places. For example, imagine a tree standing in the centre of a field, with a row of buildings at the edge of the field behind the tree. If two observers stand at the two front corners of the field, the tree will appear in front of a different building for each observer. Similarly, a nearby star's position appears different when seen from different angles.
Parallax also allows human eyes to judge distance. Each eye sees an object from a different angle. The brain compares the two pictures to judge the distance to the object. Astronomers use the same idea to calculate the distance to a star. Stars are very far away, so astronomers must look at a star from two locations as far apart as possible to get a measurement. The movement of Earth around the Sun makes this possible. By taking measurements six months apart from the same place on Earth, astronomers take measurements from locations separated by the diameter of Earth’s orbit. That is a separation of about 300 million km (186 million mi). The nearest stars will appear to shift slightly with respect to the background of more distant stars. Even so, the greatest stellar parallax is only about 0.77 seconds of arc, an amount 4,600 times smaller than a single degree. Astronomers calculate a star’s distance by dividing one by the parallax. Distances of stars are usually measured in parsecs. A parsec is 3.26 light-years, and a light-year is the distance that light travels in a year, or about 9.5 trillion km (5.9 trillion mi). Proxima Centauri, the Sun’s nearest neighbour, has a parallax of 0.77 seconds of arc. This measurement indicates that Proxima Centauri’s distance from Earth is about 1.3 parsecs, or 4.2 light -years. Because Proxima Centauri is the Sun’s nearest neighbours, it has a larger parallax than any other star.
Astronomers can measure stellar parallaxes for stars up to about 500 light-years away, which is only about 2 percent of the distance to the centre of our galaxy. Beyond that distance, the parallax angle is too small to measure.
A European Space Agency spacecraft named Hipparcos (an acronym for High Precision Parallax Collecting Satellite), launched in 1989, gave a set of accurate parallaxes across the sky that was released in 1997. This set of measurements has provided a uniform database of stellar distances for more than 100,000 stars and to some degree less accurate database of more than one million stars. These parallax measurements provide the base for measurements of the distance scale of the universe. Hipparcos data are leading to more accurate age calculations for the universe and for objects in it, especially globular clusters of stars.
Astronomers use a star’s light to determine the star’s temperature, composition, and motion. Astronomers analyse a star’s light by looking at its intensity at different wavelengths. Blue light has the shortest visible wavelengths, at about 400 nanometres. (A nanometre, abbreviated ‘nm’, is one billionth of a metre, or about one forty-thousandth of an inch.) Red light has the longest visible wavelengths, at about 650 nm. A law of radiation known as Wien's displacement law (developed by German physicist Wilhelm Wien) links the wavelength at which the most energy is given out by an object and its temperature. A star like the Sun, whose surface temperature is about 6000 K (about 5730°C or about 10,350°F), gives off the most radiation in yellow-green wavelengths, with decreasing amounts in shorter and longer wavelengths. Astronomers put filters of different standard colours on telescopes to allow only light of a particular colour from a star to pass. In this way, astronomers determine the brightness of a star at particular wavelengths. From this information, astronomers can use Wien’s law to determine the star’s surface temperature.
Astronomers can see the different wavelengths of light of a star in more detail by looking at its spectrum. The continuous rainbow of colour of a star's spectrum is crossed by dark lines, or spectral lines. In the early 19th century, German physicist Josef Fraunhofer identified such lines in the Sun's spectrum, and they are still known as Fraunhofer lines. American astronomer Annie Jump Cannon divided stars into several categories by the appearance of their spectra. She labelled them with capital letters according to how dark their hydrogen spectral lines were. Later astronomers reordered these categories according to decreasing temperature. The categories are O, B, A, F, G, K, and M, where O stars are the hottest and M stars are the coolest. The Sun is a G star. An additional spectral type, L stars, was suggested in 1998 to accommodate some cool stars studied using new infrared observational capabilities. Detailed study of spectral lines shows the physical conditions in the atmospheres of stars. Careful study of spectral lines shows that some stars have broader lines than others of the same spectral type. The broad lines indicate that the outer layers of these stars are more diffuse, meaning that these layers are larger, but spread more thinly, than the outer layers of other stars. Stars with large diffuse atmospheres are called giants. Giant stars are not necessarily more massive than other stars-the outer layers of giant stars are just more spread out.
Many stars have thousands of spectral lines from iron and other elements near iron in the periodic table. Other stars of the same temperature have very few spectral lines from such elements. Astronomers interpret these findings to mean that two different populations of stars exist. Some formed long ago, before supernovas produced the heavy elements, and others formed more recently and incorporated some heavy elements. The Sun is one of the more recent stars.
Spectral lines can also be studied to see if they change in wavelength or are different in wavelength from sources of the same lines on Earth. These studies tell us, according to the Doppler effect, how much the star is moving toward or away from us. Such studies of starlight can tell us about the orbits of stars in binary systems or about the pulsations of variable stars, for example.
Astronomers study galaxies to learn about the structure of the universe. Galaxies are huge collections of billions of stars. Our Sun is part of the Milky Way Galaxy. Galaxies also contain dark strips of dust and may contain huge black holes at their centres. Galaxies exist in different shapes and sizes. Some galaxies are spirals, some are oval, or elliptical, and some are irregular. The Milky Way is a spiral galaxy. Galaxies tend to group together in clusters.
Our Sun is only one of about 400 billion stars in our home galaxy, the Milky Way. On a dark night, far from outdoor lighting, a faint, hazy, whitish band spans the sky. This band is the Milky Way Galaxy as it appears from Earth. The Milky Way looks splotchy, with darker regions interspersed with lighter ones.
The Milky Way Galaxy is a pinwheel-shaped flattened disk about 75,000 light-years in diameter. The Sun is located on a spiral arm about two-thirds of the way out from the centre. The galaxy spins, but the centre spins faster than the arms. At Earth’s position, the galaxy makes a complete rotation about every 200 million years.
When observers on Earth look toward the brightest part of the Milky Way, which is in the constellation Sagittarius, they look through the galaxy’s disk toward its centre. This disk is composed of the stars, gas, and dust between Earth and the galactic centre. When observers look in the sky in other directions, they do not see as much of the galaxy’s gas and dust, and so can see objects beyond the galaxy more clearly.
The Milky Way Galaxy has a core surrounded by its spiral arms. A spherical cloud containing about 100 examples of a type of star cluster known as a globular cluster surrounds the galaxy. Still, farther out is a galactic corona. Astronomers are not sure what types of particles or objects occupy the corona, but these objects do exert a measurable gravitational force on the rest of the galaxy. Galaxies contain billions of stars, but the space between stars is not empty. Astronomers believe that almost every galaxy probably has a huge black hole at its centre.
The space between stars in a galaxy consists of low
- density gas and dust. The dust is largely carbon given off by red-giant stars. The gas is largely hydrogen, which accounts for 90 percent of the atoms in the universe. Hydrogen exists in two main forms in the universe. Astronomers give complete hydrogen atoms, with a nucleus and an electron, a designation of the Roman numeral I, or HI. Ionized hydrogen, hydrogen made up of atoms missing their electrons, is given the designation II, or HII. Clouds, or regions, of both types of hydrogen exist between the stars. HI regions are too cold to produce visible radiation, but they do emit radio waves that are useful in measuring the movement of gas in our own galaxy and in distant galaxies. The HII regions form around hot stars. These regions emit diffuse radiation in the visual range, as well as in the radio, infrared, and ultraviolet ranges. The cloudy light from such regions forms beautiful nebulas such as the Great Orion Nebula.
Astronomers have located more than 100 types of molecules in interstellar space. These molecules occur only in trace amounts among the hydrogens. Still, astronomers can use these molecules to map galaxies. By measuring the density of the molecules throughout a galaxy, astronomers can get an idea of the galaxy’s structure. interstellar dust sometimes gathers to form dark nebulae, which appear in silhouette against background gas or stars from Earth. The Horsehead Nebula, for example, is the silhouette of interstellar dust against a background HI region.
The first known black holes were the collapsed cores of supernova stars, but astronomers have since discovered signs of much larger black holes at the centres of galaxies. These galactic black holes contain millions of times as much mass as the Sun. Astronomers believe that huge black holes such as these provide the energy of mysterious objects called quasars. Quasars are very distant objects that are moving away from Earth at high speed. The first ones discovered were very powerful radio sources, but scientists have since discovered quasars that don’t strongly emit radio waves. Astronomers believe that almost every galaxy, whether spiral or elliptical, has a huge black hole at its centre.
Astronomers look for galactic black holes by studying the movement of galaxies. By studying the spectrum of a galaxy, astronomers can tell if gas near the centre of the galaxy is rotating rapidly. By measuring the speed of rotation and the distance from various points in the galaxy to the centre of the galaxy, astronomers can determine the amount of mass in the centre of the galaxy. Measurements of many galaxies show that gas near the centre is moving so quickly that only a black hole could be dense enough to concentrate so much mass in such a small space. Astronomers suspect that a significant black hole occupies even the centre of the Milky Way. The clear images from the Hubble Space Telescope have allowed measurements of motions closer to the centres of galaxies than previously possible, and have led to the confirmation in several cases that giant black holes are present.
Galaxies are classified by shape. The three types are spiral, elliptical, and irregular. Spiral galaxies consist of a central mass with one, two, or three arms that spiral around the centre. An elliptical galaxy is oval, with a bright centre that gradually, evenly dims to the edges. Irregular galaxies are not symmetrical and do not look like spiral or elliptical galaxies. Irregular galaxies vary widely in appearance. A galaxy that has a regular spiral or elliptical shape but has, some special oddity is known as a peculiar galaxy. For example, some peculiar galaxies are stretched and distorted from the gravitational pull of a nearby galaxy.
Spiral galaxies are flattened pinwheels in shape. They can have from one to three spiral arms coming from a central core. The Great Andromeda Spiral Galaxy is a good example of a spiral galaxy. The shape of the Milky Way is not visible from Earth, but astronomers have measured that the Milky Way is also a spiral galaxy. American astronomer Edwin Hubble further classified spirals galaxies by the tightness of their spirals. In order of increasingly open arms, Hubble’s types are Sa, Sb., and Sc. Some galaxies have a straight, bright, bar-shaped feature across their centre, with the spiral arms coming off the bar or off a ring around the bar. With a capital B for the bar, the Hubble types of these galaxies are SBa, SBb, and Sbc.
Many clusters of galaxies have giant elliptical galaxies at their centres. Smaller elliptical galaxies, called dwarf elliptical galaxies, are much more common than giant ones. Most of the two dozen galaxies in the Milky Way’s Local Group of galaxies are dwarf elliptical galaxies.
Astronomers classify elliptical galaxies by how oval they look, ranging from E0 for very round to E3 for intermediately oval to E7 for extremely elongated. The galaxy class E7 is also called S0, which is also known as a lenticular galaxy, a shape with an elongated disk but no spiral arms. Because astronomers can see other galaxies only from the perspective of Earth, the shape astronomers see is not necessarily the exact shape of a galaxy. For instance, they may be viewing it from an end, and not from above or below.
Some galaxies have no structure, while others have some trace of structure but do not fit the spiral or elliptical classes. All of these galaxies are called irregular galaxies. The two small galaxies that are satellites to the Milky Way Galaxy are both irregular. They are known as the Magellanic Clouds. The Large Magellanic Cloud shows signs of having a bar in its centre. The Small Magellanic Cloud is more formless. Studies of stars in the Large and Small Magellanic Clouds have been fundamental for astronomers’ understanding of the universe. Each of these galaxies provides groups of stars that are all at the same distance from Earth, allowing astronomers to compare the absolute brightness of these stars.
In the late 1920s American astronomer Edwin Hubble discovered that all but the nearest galaxies to us are receding, or moving away from us. Further, he found that the farther away from Earth a galaxy is, the faster it is receding. He made his discovery by taking spectra of galaxies and measuring the amount by which the wavelengths of spectral lines were shifted. He measured distance in a separate way, usually from studies of Cepheid variable stars. Hubble discovered that essentially all the spectra of all the galaxies were shifted toward the red, or had red-shifts. The red-shifts of galaxies increased with increasing distance from Earth. After Hubble’s work, other astronomers made the connection between red-shift and velocity, showing that the farther a galaxy is from Earth, the faster it moves away from Earth. This idea is called Hubble’s law and is the basis for the belief that the universe is uniformly expanding. Other uniformly expanding three-dimensional objects, such as a rising cake with raisins in the batter, also demonstrate the consequence that the more distant objects (such as the other raisins with respect to any given raisin) appear to recede more rapidly than nearer ones. This consequence is the result of the increased amount of material expanding between these more distant objects.
Hubble's law state that there is a straight-line, or linear, relationship between the speed at which an object is moving away from Earth and the distance between the object and Earth. The speed at which an object is moving away from Earth is called the object’s velocity of recession. Hubble’s law indicates that as velocity of recession increases, distance increases by the same proportion. Using this law, astronomers can calculate the distance to the most-distant galaxies, given only measurements of their velocities calculated by observing how much their light is shifted. Astronomers can accurately measure the red-shifts of objects so distant that the distance between Earth and the objects cannot be measured by other means.
The constant of proportionality that relates velocity to distance in Hubble's law is called Hubble's constant, or H. Hubble's law is often written v Hd, or velocity equals Hubble's constant multiplied by distance. Thus determining Hubble's constant will give the speed of the universe's expansion. The inverse of Hubble’s constant, or 1/H, theoretically provides an estimate of the age of the universe. Astronomers now believe that Hubble’s constant has changed over the lifetime of the universe, however, so estimates of expansion and age must be adjusted accordingly.
The value of Hubble’s constant probably falls between sixty-four and 78 kilometres per second per mega-parsec (between forty and 48 miles per second per mega-parsec). A mega-parsec is one million parsecs and a parsec is 3.26 light-years. The Hubble Space Telescope studied Cepheid variables in distant galaxies to get an accurate measurement of the distance between the stars and Earth to refine the value of Hubble’s constant. The value they found is 72 kilometres per second per mega-parsec (45 miles per second per mega-parsec), with an uncertainty of only 10 percent
The actual age of the universe depends not only on Hubble's constant but also on how much the gravitational pull of the mass in the universe slows the universe’s expansion. Some data from studies that use the brightness of distant supernovas to assess distance indicate that the universe's expansion is speeding up instead of slowing. Astronomers invented the term ‘dark energy’ for the unknown cause of this accelerating expansion and are actively investigating these topics. The ultimate goal of astronomers is to understand the structure, behaviour, and evolution of all of the matter and energy that exist. Astronomers call the set of all matter and energy the universe. The universe is infinite in space, but astronomers believe it does have a finite age. Astronomers accept the theory that about fourteen billion years ago the universe began as an explosive event resulting in a hot, dense, expanding sea of matter and energy. This event is known as the big bang Astronomers cannot observe that far back in time. Many astronomers believe, however, the theory that within the first fraction of a second after the big bang, the universe went through a tremendous inflation, expanding many times in size, before it resumed a slower expansion.
As the universe expanded and cooled, various forms of elementary particles of matter formed. By the time the universe was one second old, protons had formed. For approximately the next 1,000 seconds, in the era of nucleosynthesis, all the nuclei of deuterium (hydrogen with both a proton and neutron in the nucleus) that are present in the universe today formed. During this brief period, some nuclei of lithium, beryllium, and helium formed as well.
When the universe was about one million years old, it had cooled to about 3000 K (about 3300°C or about 5900°F). At that temperature, the protons and heavier nuclei formed during nucleosynthesis could combine with electrons to form atoms. Before electrons combined with nuclei, the travel of radiation through space was very difficult. Radiation in the form of photons (packets of light energy) could not travel very far without colliding with electrons. Once protons and electrons combined to form hydrogen, photons became able to travel through space. The radiation carried by the photons had the characteristic spectrum of a hot gas. Since the time this radiation was first released, it has cooled and is now 3 K (-270°C or-450°F). It is called the primeval background radiation and has been definitively detected and studied, first by radio telescopes and then by the Cosmic Background Explorer (COBE) and Wilkinson Microwave Anisotropy Probe (WMAP) spacecrafts. COBE, WMAP, and ground-based radio telescopes detected tiny deviations from uniformity in the primeval background radiation; these deviations may be the seeds from which clusters of galaxies grew.
The gravitational force from invisible matter, known as dark matter, may have helped speed the formation of structure in the universe. Observations from the Hubble Space Telescope have revealed older galaxies than astronomers expected, reducing the interval between the big bang and the formation of galaxies or clusters of galaxies.
From about two billion years after the big bang for another two billion years, quasars formed as active giant black holes in the cores of galaxies. These quasars gave off radiation as they consumed matter from nearby galaxies. Few quasars appear close to Earth, so quasars must be a feature of the earlier universe.
A population of stars formed out of the interstellar gas and dust that contracted to form galaxies. This first population, known as Population II, was made up almost entirely of hydrogen and helium. The stars that formed evolved and gave out heavier elements that were made through fusion in the stars’ cores or that was formed as the stars exploded as supernovas. The later generation of stars, to which the Sun belongs, is known as Population I and contains heavy elements formed by the earlier population. The Sun formed about five billion years ago and is almost halfway through its 11-billion-year lifetime
About 4.6 billion years ago, our solar system formed. The oldest fossils of a living organism date from about 3.5 billion years ago and represent Cyanobacteria. Life evolved, and sixty-five million years ago, the dinosaurs and many other species were extinguished, probably from a catastrophic meteor impact. Modern humans evolved no earlier than a few hundred thousand years ago, a blink of an eye on the cosmic timescale.
Will the universe expand forever or eventually stop expanding and collapse in on itself? Jay M. Pasachoff, professor of astronomy at Williams College in Williamstown, Massachusetts, confronts this question in this discussion of cosmology. Whether the universe will go on expanding forever, depends on whether there is enough critical density to halt or reverse the expansion, and the answer to that question may, in turn, depend on the existence of something the German-born American physicist Albert Einstein once labelled the cosmological constant.
New technology allows astronomers to peer further into the universe than ever before. The science of cosmology, the study of the universe as a whole, has become an observational science. Scientists may now verify, modify, or disprove theories that were partially based on guesswork.
In the 1920s, the early days of modern cosmology, it took an astronomer all night at a telescope to observe a single galaxy. Current surveys of the sky will likely compile data for a million different galaxies within a few years. Building upon advances in cosmology over the past century, our understanding of the universe should continue to accelerate
Modern cosmology began with the studies of Edwin Hubble, who measured the speeds that galaxies move toward or away from us in the mid-1920s. By observing red-shift-the change in wavelength of the light that galaxies give off as they move away from us-Hubble realized that though the nearest galaxies are approaching us, all distant galaxies are receding. The most-distant galaxies are receding most rapidly. This observation is consistent with the characteristics of an expanding universe. Since 1929 an expanding universe has been the first and most basic pillar of cosmology.
In 1990 the National Aeronautics and Space Administration (NASA) launched the Hubble Space Telescope (HST), named to honour the pioneer of cosmology. Appropriately, determining the rate at which the universe expands was one of the telescope’s major tasks.
One of the HST’s key projects was to study Cepheid variables (stars that varies greatly in brightness) and to measure distances in space. Another set of Hubble’s observations focuses on supernovae, exploding stars that can be seen at very great distances because they are so bright. Studies of supernovae in other galaxies reveal the distances to those galaxies.
The term big bang refers to the idea that the expanding universe can be traced back in time to an initial explosion. In the mid-1960s, physicists found important evidence of the big bang when they detected faint microwave radiation coming from every part of the sky. Astronomers think this radiation originated about 300,000 years after the big bang, when the universe thinned enough to become transparent. The existence of cosmic microwave background radiation, and its interpretation, is the second pillar of modern cosmology.
Also in the 1960s, astronomers realized that the lightest of the elements, including hydrogen, helium, lithium, and boron, were formed mainly at the time of the big bang. What is most important, deuterium (the form of hydrogen with an extra neutron added to normal hydrogen's single proton) was formed only in the era of nucleosynthesis? This era started about one second after the universe was formed and made up the first three minutes or so after the big bang. No sources of deuterium are known since that early epoch. The current ratio of deuterium to regular hydrogen depends on how dense the universe was at that early time, so studies of the deuterium that can now be detected indicate how much matter the universe contains. These studies of the origin of the light elements are the third pillar of modern cosmology.
Until recently many astronomers disagreed on whether the universe was expected to expand forever or eventually stop expanding and collapse in on itself in a ‘big crunch.’
At the General Assembly of the International Astronomical Union (IAU) held in August 2000, a consistent picture of cosmology emerged. This picture depends on the current measured value for the expansion rate of the universe and on the density of the universe as calculated from the abundances of the light elements. The most recent studies of distant supernovae seem to show that the universe's expansion is accelerating, not slowing. Astronomers have recently proposed a theoretical type of negative energy-which would provide a force that opposes the attraction of gravity-to explain the accelerating universe.
For decades scientists have debated the rate at which the universe is expanding. We know that the further away a galaxy is, the faster it moves away from us. The question is: How fast are galaxies receding for each unit of distance they are away from us? The current value, as announced at the IAU meeting, is 75 km/s/Mpc, that is, for each mega-parsec of distance from us (where each mega-parsec is 3.26 million light-years), the speed of expansion increases by 75 kilometres per second.
What’s out there, exactly?
In the picture of expansion held until recently, astronomers thought the universe contained just enough matter and energy so that it would expand forever but expand at a slower and slower rate as time went on. The density of matter and energy necessary for this to happen is known as the critical density.
Astronomers now think that only 5 percent or so of the critical density of the universe is made of ordinary matter. Another 25 percent or so of the critical density is made of dark matter, a type of matter that has gravity but that has not been otherwise detected. The accelerating universe, further, shows that the remaining 70 percent of the critical density is made of a strange kind of energy, perhaps that known as the cosmological constant, an idea tentatively invoked and then abandoned by Albert Einstein in equations for his general theory of relativity.
Some may be puzzled: Didn't we learn all about the foundations of physics when we were still at school? The answer is ‘yes’ or ‘no’, depending on the interpretation. We have become acquainted with concepts and general relations that enable us to comprehend an immense range of experiences and make them accessible to mathematical treatment. In a certain sense these concepts and relations are probably even final. This is true, for example, of the laws of light refraction, of the relations of classical thermodynamics as far as it is based on the concepts of pressure, volume, temperature, heat and work, and of the hypothesis of the nonexistence of a perpetual motion machine.
What, then, impels us to devise theory after theory? Why do we devise theories at all? The answer to the latter question is simple: Because we enjoy ‘comprehending’, i.e., reducing phenomena by the process of logic to something already known or (apparently) evident. New theories are first of all necessary when we encounter new facts that cannot be ‘explained’ by existing theories. Nevertheless, this motivation for setting up new theories is, so to speak, trivial, imposed from without. There is another, more subtle motive of no less importance. This is the striving toward unification and simplification of the premises of the theory as a whole (i.e., Mach's principle of economy, interpreted as a logical principle).
There exists a passion for comprehension, just as there exists a passion for music. That passion is altogether common in children, but gets lost in most people later on. Without this passion, there would be neither mathematics nor natural science. Time and again the passion for understanding has led to the illusion that man is able to comprehend the objective world rationally, by pure thought, without any empirical foundations-in short, by metaphysics. I believe that every true theorist is a kind of tamed metaphysicist, no matter how pure a
‘positivist’, he may fancy himself. The metaphysicist believes that the logically simple are also the real. The tamed metaphysicist believes that not all that is logically simple is embodied in experienced reality, but that the totality of all sensory experience can be ‘comprehended’ on the basis of a conceptual system built on premises of great simplicity. The skeptic will say that this is a ‘miracle creed’. Admittedly so, but it is a miracle creed that has been borne out to an amazing extent by the development of science.
The rise of atomism is a good example. How may Leucippus have conceived this bold idea? When water freezes and becomes ice-apparently something entirely different from water-why is it that the thawing of the ice forms something that seems indistinguishable from the original water? Leucippus is puzzled and looks for an ‘explanation’. He is driven to the conclusion that in these transitions the ‘essence’, of the thing has not changed at all. Maybe the thing consists of immutable particles and the change is only a change in their spatial arrangement. Could it not be that the same is true of all material objects that emerge again and again with nearly identical qualities?
This idea is not entirely lost during the long hibernation of occidental thought. Two thousand years after Leucippus, Bernoulli wonders why gas exerts pressure on the walls of a container. Should this be ‘explained’ by mutual repulsion of the parts of the gas, in the sense of Newtonian mechanics? This hypothesis appears absurd, for the gas pressure depends on the temperature, all other things being equal. To assume that the Newtonian forces of interaction depend on temperature is contrary to the spirit of Newtonian mechanics. Since Bernoulli is aware of the concept of atomism, he is bound to conclude that the atoms (or molecules) collide with the walls of the container and in doing so exert pressure. After all, one has to assume that atoms are in motion; how else can one account for the varying temperature of gases?
A simple mechanical consideration shows that this pressure depends only on the kinetic energy of the particles and on their density in space. This should have led the physicists of that age to the conclusion that heat consists in random motion of the atoms. Had they taken this consideration as seriously as it deserved to be taken, the development of the theory of heat-in particular the discovery of the equivalence of heat and mechanical energy-would have been considerably facilitated.
This example is meant to illustrate two things. The theoretical idea (atomism in this case) does not arise apart and independent of experience; nor can it be derived from experience by a purely logical procedure. It is produced by a creative act. Once a theoretical idea has been acquired, one does well to hold fast to it until it leads to an untenable conclusion.
In Newtonian physics the elementary theoretical concept on which the theoretical description of material bodies is based is the material point, or particle. Thus, matter is considered theoretically to be discontinuous. This makes it necessary to consider the action of material points on one another as ‘action at a distance’. Since the latter concept seems quite contrary to everyday experience, it is only natural that the contemporaries of Newton-and in fact, Newton himself found it difficult to accept. Owing to the almost miraculous success of the Newtonian system, however, the succeeding generations of physicists became used to the idea of action at a distance. Any doubt was buried for a long time to come.
All the same, when, in the second half of the 19th century, the laws of electrodynamics became known, it turned out that these laws could not be satisfactorily incorporated into the Newtonian system. It is fascinating to muse: Would Faraday have discovered the law of electromagnetic induction if he had received a regular college education? Unencumbered by the traditional way of thinking, he felt that the introduction of the ‘field’ as an independent element of reality helped him to coordinate the experimental facts. It was Maxwell who fully comprehended the significance of the field concept; he made the fundamental discovery that the laws of electrodynamics found their natural expression in the differential equations for the electric and magnetic fields. These equations implied the existence of waves, whose properties corresponded to those of light as far as they were known at that time.
This incorporation of optics into the theory of electromagnetism represents one of the greatest triumphs in the striving toward unification of the foundations of physics; Maxwell achieved this unification by purely theoretical arguments, long before it was corroborated by Hertz' experimental work. The new insight made it possible to dispense with the hypothesis of action at a distance, at least in the realm of electromagnetic phenomena; the intermediary field now appeared as the only carrier of electromagnetic interaction between bodies, and the field's behaviour was completely determined by contiguous processes, expressed by differential equations.
Now a question arose: Since the field exists even in a vacuum, should one conceive of the field as a state of a ‘carrier’, or should it be endowed with an independent existence not reducible to anything else? In other words, is there an ‘ether’ which carries the field; the ether being considered in the undulatory state, for example, when it carries light waves?
The question has a natural answer: Because one cannot dispense with the field concept, not introducing in addition a carrier with hypothetical properties is preferable. However, the pathfinder who first recognized the indispensability of the field concept were still too strongly imbued with the mechanistic tradition of thought to accept unhesitatingly this simple point of view. Nevertheless, in the course of the following decades this view imperceptibly took hold.
The introduction of the field as an elementary concept gave rise to an inconsistency of the theory as a whole. Maxwell's theory, although adequately describing the behaviour of electrically charged particles in their interaction with one another, does not explain the behaviours of electrical densities, i.e., it does not provide a theory of the particles themselves. They must therefore be treated as mass points on the basis of the old theory. The combination of the idea of a continuous field with that of material points discontinuous in space appears inconsistent. A consistent field theory requires continuity of all elements of the theory, not only in time but also in space, and in all points of space. Hence the material particle has no place as a fundamental concept in a field theory. Thus, even apart from the fact that gravitation is not included. Maxwell’s electrodynamics cannot be considered a complete theory.
Maxwell's equations for empty space remain unchanged if the spatial coordinates and the time are subjected to a particular linear transformations-the Lorentz transformations (‘covariance’ with respect to Lorentz transformations). Covariance also holds, of course, for a transformation that is composed of two or more such transformations; this is called the ‘group’ property of Lorentz transformations.
Maxwell's equations imply the ‘Lorentz group’, but the Lorentz group does not imply Maxwell's equations. The Lorentz group may effectively be defined independently of Maxwell's equations as a group of linear transformations that leave a particular value of the velocity-the velocity of light-invariant. These transformations hold for the transition from one ‘inertial system to another that is in uniform motion relative to the first. The most conspicuous novel property of this transformation group is that it does away with the absolute character of the concept of simultaneity of events distant from each other in space. On this account it is to be expected that all equations of physics are covariant with respect to Lorentz transformations (special theory of relativity). Thus it came about that Maxwell's equations led to a heuristic principle valid far beyond the range of the applicability or even validity of the equations themselves.
Special relativity has this in common with Newtonian mechanics: The laws of both theories are supposed to hold only with respect to certain coordinate systems: those known as ‘inertial systems’. An inertial system is a system in a state of motion such that ‘force-free’ material points within it are not accelerated with respect to the coordinate system. However, this definition is empty if there is no independent means for recognizing the absence of forces. Nonetheless, such a means of recognition does not exist if gravitation is considered as a ‘field’.
Let ‘A’ be a system uniformly accelerated with respect to an ‘inertial system’ I. Material points, not accelerated with respect to me, are accelerated with respect to ‘A’, the acceleration of all the points being equal in magnitude and direction. They behave as if a gravitational field exists with respect to ‘A’, for it is a characteristic property of the gravitational field that the acceleration is independent of the particular nature of the body. There is no reason to exclude the possibility of interpreting this behaviour as the effect of a ‘true’ gravitational field (principle of equivalence). This interpretation implies that ‘A’ is an ‘inertial system,’ even though it is accelerated with respect to another inertial system. (It is essential for this argument that the introduction of independent gravitational fields is considered justified even though no masses generating the field are defined. Therefore, to Newton such an argument would not have appeared convincing.) Thus the concepts of inertial system, the law of inertia and the law of motion are deprived of their concrete meaning-not only in classical mechanics but also in special relativity. Moreover, following up this train of thought, it turns out that with respect to A time cannot be measured by identical clocks; effectively, even the immediate physical significance of coordinate differences is generally lost. In view of all these difficulties, should one not try, after all, to hold on to the concept of the inertial system, relinquishing the attempt to explain the fundamental character of the gravitational phenomena that manifest themselves in the Newtonian system as the equivalence of inert and gravitational mass? Those who trust in the comprehensibility of nature must answer: No.
This is the gist of the principle of equivalence: In order to account for the equality of inert and gravitational mass within the theory admitting nonlinear transformations of the four coordinates is necessary. That is, the group of Lorentz transformations and hence the set of the "permissible" coordinate systems has to be extended.
What group of coordinate transformations can then be substituted for the group of Lorentz transformations? Mathematics suggests an answer that is based on the fundamental investigations of Gauss and Riemann: namely, that the appropriate substitute is the group of all continuous (analytical) transformations of the coordinates. Under these transformations the only thing that remains invariant is the fact that neighbouring points have nearly the same coordinates; the coordinate system expresses only the topological order of the points in space (including its four-dimensional character). The equations expressing the laws of nature must be covariant with respect to all continuous transformations of the coordinates. This is the principle of general relativity.
The procedure just described overcomes a deficiency in the foundations of mechanics that had already been noticed by Newton and was criticized by Leibnitz and, two centuries later, by Mach: Inertia resists acceleration, but acceleration relative to what? Within the frame of classical mechanics the only answer is: Inactivity resists velocity relative to distances. This is a physical property of space-space acts on objects, but objects do not act on space. Such is probably the deeper meaning of Newton's assertion spatium est absolutum (space is absolute). Nevertheless, the idea disturbed some, in particular Leibnitz, who did not ascribe an independent existence to space but considered it merely a property of ‘things’ (contiguity of physical objects). Had his justified doubts won out at that time, it hardly would have been a boon to physics, for the empirical and theoretical foundations necessary to follow up his idea was not available in the 17th century.
According to general relativity, the concept of space detached from any physical content does not exist. The physical reality of space is represented by a field whose components are continuous functions of four independent variables—the coordinates of space and time. It is just this particular kind of dependence that expresses the spatial character of physical reality.
Since the theory of general relativity implies the representation of physical reality by a continuous field, the concept of particles or material points cannot . . . play a fundamental part, nor can the concept of motion. The particle can only appear as a limited region in space in which the field strength or the energy density is particularly high.
A relativistic theory has to answer two questions: (1) What is the mathematical character of the field? What equations hold for this field?
Concerning the first question: From the mathematical point of view the field is essentially characterized by the way its components transform if a coordinate transformation is applied. Concerning the second (2) question: The equations must determine the field to a sufficient extent while satisfying the postulates of general relativity. Whether or not this requirement can be satisfied, depends on the choice of the field-type.
The attempts to comprehend the correlations among the empirical data on the basis of such a highly abstract program may at first appear almost hopeless. The procedure amounts, in fact, to putting the question: What most simple property can be required from what most simple object (field) while preserving the principle of general relativity? Viewed in formal logic, the dual character of the question appears calamitous, quite apart from the vagueness of the concept ‘simple’. Moreover, as for physics there is nothing to warrant the assumption that a theory that is ‘logically simple’ should also be ‘true’.
Yet every theory is speculative. When the basic concepts of a theory are comparatively ‘close to experience’ (e.g., the concepts of force, pressures, mass), its speculative character is not so easily discernible. If, however, a theory is such as to require the application of complicated logical processes in order to reach conclusions from the premises that can be confronted with observation, everybody becomes conscious of the speculative nature of the theory. In such a case an almost irresistible feeling of aversion arises in people who are inexperienced in epistemological analysis and who are unaware of the precarious nature of theoretical thinking in those fields with which they are familiar.
On the other hand, it must be conceded that a theory has an important advantage if its basic concepts and fundamental hypotheses are ‘close to experience’, and greater confidence in such a theory is justifiable. There is less danger of going completely astray, particularly since it takes so much less time and effort to disprove such theories by experience. Yet ever more, as the depth of our knowledge increases, we must give up this advantage in our quest for logical simplicity and uniformity in the foundations of physical theory. It has to be admitted that general relativity has gone further than previous physical theories in relinquishing ‘closeness to experience’ of fundamental concepts in order to attain logical simplicity. This holds all ready for the theory of gravitation, and it is even more true of the new generalization, which is an attempt to comprise the properties of the total field. In the generalized theory the procedure of deriving from the premises of the theory conclusions that can be confronted with empirical data is so difficult that so far no such result has been obtained. In favour of this theory are, at this point, its logical simplicity and its ‘rigidity’. Rigidity means here that the theory is either true or false, but not modifiable.
The greatest inner difficulty impeding the development of the theory of relativity is the dual nature of the problem, indicated by the two questions we have asked. This duality is the reason the development of the theory has taken place in two steps so widely separated in time. The first of these steps, the theory of gravitation, is based on the principle of equivalence discussed above and rests on the following consideration: According to the theory of special relativity, light has a constant velocity of propagation. If a light ray in a vacuum starts from a point, designated by the coordinates x1, x2 and x3 in a three-dimensional coordinate system, at the time x4, it spreads as a spherical wave and reaches a neighbouring point (x1 + dx1, x2 + dx2, x3 + dx3) at the time x4 + dx4. Introducing the velocity of light, c, we write the expression:
This expression represents an objective relation between neighbouring space-time points in four dimensions, and it holds for all inertial systems, provided the coordinate transformations are restricted to those of special relativity. The relation loses this form, however, if arbitrary continuous transformations of the coordinates are admitted in accordance with the principle of general relativity. The relation then assumes the more general form:
Σik gik dxi dxk=0
The gik are certain functions of the coordinates that transform in a definite way if a continuous coordinate transformation is applied. According to the principle of equivalence, these gik functions describe a particular kind of gravitational field: a field that can be obtained by transformation of ‘field-free’ space. The gik satisfies a particular law of transformation. Mathematically speaking, they are the components of a ‘tensor’ with a property of symmetry that is preserved in all transformations; the symmetrical property is expressed as follows:
gik=gki
The idea suggests itself: May we not ascribe objective meaning to such a symmetrical tensor, even though the field cannot be obtained from the empty space of special relativity by a mere coordinate transformation? Although we cannot expect that such a symmetrical tensor will describe the most general field, it may describe the particular case of the ‘pure gravitational field’. Thus it is evident what kind of field, at least for a special case, general relativity has to postulate: a symmetrical tensor field.
Hence only the second question is left: What kind of general covariant field law can be postulated for a symmetrical tensor field?
This question has not been difficult to answer in our time, since the necessary mathematical conceptions were already here in the form of the metric theory of surfaces, created a century ago by Gauss and extended by Riemann to manifolds of an arbitrary number of dimensions. The result of this purely formal investigation has been amazing in many respects. The differential equations that can be postulated as field law for gik cannot be of lower than second order, i.e., they must at least contain the second derivatives of the gik with respect to the coordinates. Assuming that no higher than second derivatives appear in the field law, it is mathematically determined by the principle of general relativity. The system of equations can be written in the form: Rik = 0. The Rik transforms in the same manner as the gik, i.e., they too form a symmetrical tensor.
These differential equations completely replace the Newtonian theory of the motion of celestial bodies provided the masses are represented as singularities of the field. In other words, they contain the law of force as well as the law of motion while eliminating ‘inertial systems’.
The fact that the masses appear as singularities indicate that these masses themselves cannot be explained by symmetrical gik fields, or ‘gravitational fields’. Not even the fact that only positive gravitating masses exist can be deduced from this theory. Evidently a complete relativistic field theory must be based on a field of more complex nature, that is, a generalization of the symmetrical tensor field.
The first observation is that the principle of general relativity imposes exceedingly strong restrictions on the theoretical possibilities. Without this restrictive principle hitting on the gravitational equations would be practically impossible for anybody, not even by using the principle of special relativity, even though one knows that the field has to be described by a symmetrical tensor. No amount of collection of facts could lead to these equations unless the principles of general relativity were used. This is the reason that all attempts to obtain a deeper knowledge of the foundations of physics seem doomed to me unless the basic concepts are in accordance with general relativity from the beginning. This situation makes it difficult to use our empirical knowledge, however comprehensive, in looking for the fundamental concepts and relations of physics, and it forces us to apply free speculation to a much greater extent than is presently assumed by most physicists. One may not see any reason to assume that the heuristic significance of the principle of general relativity is restricted to gravitation and that the rest of physics can be dealt with separately on the basis of special relativity, with the hope that later as a resultant circumstance brings about the whole that may be fitted consistently into a general relativistic scheme. One is to think that such an attitude, although historically understandable, can be objectively justified. The comparative smallness of what we know today as gravitational effects is not a conclusive reason for ignoring the principle of general relativity in theoretical investigations of a fundamental character. In other words, I do not believe that asking it is justifiable: What would physics look like without gravitation?
The second point we must note is that the equations of gravitation are ten differential equations for the ten components of the symmetrical tensor gik. In the case of a non-generalized relativity theory, a system is ordinarily not over determined if the number of equations is equal to the number of unknown functions. The manifold of solutions is such that within the general solution a certain number of functions of three variables can be chosen arbitrarily. For a general relativistic theory this cannot be expected as a matter of course. Free choice with respect to the coordinate system implies that out of the ten functions of a solution, or components of the field, four can be made to assume prescribed values by a suitable choice of the coordinate system. In other words, the principle of general relativity implies that the number of functions to be determined by differential equations is not ten but 10-4=6. For these six functions only six independent differential equations may be postulated. Only six out of the ten differential equations of the gravitational field ought to be independent of each other, while the remaining four must be connected to those six by means of four relations (identities). In earnest there exist among the left-hand sides, Rik, of the ten gravitational equations four identities ’Bianchi's identities’-which assure their ‘compatibility’.
In a case like this-when the number of field variables is equal to the number of differential equations-compatibility is always assured if the equations can be obtained from a variational principle. This is unquestionably the case for the gravitational equations.
However, the ten differential equations cannot be entirely replaced by six. The system of equations is verifiably ‘over determined’, but due to the existence of the identities it is over determined in such a way that its compatibility is not lost, i.e., the manifold of solutions is not critically restricted. The fact that the equations of gravitation imply the law of motion for the masses is intimately connected with this (permissible) over determination.
After this preparation understanding the nature of the present investigation without entering into the details of its mathematics is now easy. The problem is to set up a relativistic theory for the total field. The most important clue to its solution is that there exists already the solution for the special case of the pure gravitational field. The theory we are looking for must therefore be a generalization of the theory of the gravitational field. The first question is: What is the natural generalization of the symmetrical tensor field?
This question cannot be answered by itself, but only in connection with the other question: What generalization of the field is going to provide the most natural theoretical system? The answer on which the theory under discussion is based is that the symmetrical tensor field must be replaced by a non-symmetrical one. This means that the condition gik = gki for the field components must be dropped. In that case the field has sixteen instead of ten independent components.
There remains the task of setting up the relativistic differential equations for a non-symmetrical tensor field. In the attempt to solve this problem one meets with a difficulty that does not arise in the case of the symmetrical field. The principle of general relativity does not suffice to determine completely the field equations, mainly because the transformation law of the symmetrical part of the field alone does not involve the components of the anti-symmetrical part or vice versa. Probably this is the reason that this kind of generalization of the field has been hardly ever tried before. The combination of the two parts of the field can only be shown to be a natural procedure if in the formalism of the theory only the total field plays a role, and not the symmetrical and anti-symmetrical parts separately.
It turned out that this requirement can actively be satisfied in a natural way. Nonetheless, even this requirement, together with the principle of general relativity, is still not sufficient to determine uniquely the field equations. Let us remember that the system of equations must satisfy a further condition: the equations must be compatible. It has been mentioned above that this condition is satisfied if the equations can be derived from a variational principle.
This has rightfully been achieved, although not in so natural a way as in the case of the symmetrical field. It has been disturbing to find that it can be achieved in two different ways. These variational principles furnished two systems of equations-let us denote them by E1 and E2-which were different from each other (although only so), each of them exhibiting specific imperfections. Consequently even the condition of compatibility was insufficient to determine the system of equations uniquely.
It was, in fact, the formal defects of the systems E1 and E2 out whom indicated a possible way. There exists a third system of equations, E3, which is free of the formal defects of the systems E1 and E2 and represents a combination of them in the sense that every solution of E3 is a solution of E1 as well as of E2. This suggests that E3 may be the system for which we have been looking. Why not postulate E3, then, as the system of equations? Such a procedure is not justified without further analysis, since the compatibility of E1 and that of E2 does not imply compatibility of the stronger system E3, where the number of equations exceeds the number of field components by four.
An independent consideration shows that irrespective of the question of compatibility the stronger system, E3, is the only really natural generalization of the equations of gravitation.
It seems, nonetheless, that E3 is not a compatible system in the same sense as are the systems E1 and E2, whose compatibility is assured by a sufficient number of identities, which means that every field that satisfies the equations for a definite value of the time has a continuous extension representing a solution in four-dimensional space. The system E3, however, is not extensible in the same way. Using the language of classical mechanics, we might say: In the case of the system E3 the ‘initial condition’ cannot be freely chosen. What really matter is the answer to the question: Is the manifold of solutions for the system E3 as extensive as must be required for a physical theory? This purely mathematical problem is as yet unsolved.
The skeptic will say: "It may be true that this system of equations is reasonable from a logical standpoint. However, this does not prove that it corresponds to nature." You are right, dear skeptic. Experience alone can decide on truth. Yet we have achieved something if we have succeeded in formulating a meaningful and precise question. Affirmation or refutation will not be easy, in spite of an abundance of known empirical facts. The derivation, from the equations, of conclusions that can be confronted with experience will require painstaking efforts and probably new mathematical methods.
Schrödinger's mathematical description of electron waves found immediate acceptance. The mathematical description matched what scientists had learned about electrons by observing them and their effects. In 1925, a year before Schrödinger published his results, German-British physicist Max Born and German physicist Werner Heisenberg developed a mathematical system called matrix mechanics. Matrix mechanics also succeeded in describing the structure of the atom, but it was totally theoretical. It gave no picture of the atom that physicists could verify observationally. Schrödinger's vindication of de Broglie's idea of electron waves immediately overturned matrix mechanics, though later physicists showed that wave mechanics are equivalent to matrix mechanics.
To solve these problems, mathematicians use calculus, which deals with continuously changing quantities, such as the position of a point on a curve. Its simultaneous development in the 17th century by English mathematician and physicist Isaac Newton and German philosopher and mathematician Gottfried Wilhelm Leibniz enabled the solution of many problems that had been insoluble by the methods of arithmetic, algebra, and geometry. Among the advances that calculus helped develop were the determinations of Newton’s laws of motion and the theory of electromagnetism.
The physical sciences investigate the nature and behaviour of matter and energy on a vast range of size and scale. In physics itself, scientists study the relationships between matter, energy, force, and time in an attempt to explain how these factors shape the physical behaviour of the universe. Physics can be divided into many branches. Scientists study the motion of objects, a huge branch of physics known as mechanics that involves two overlapping sets of scientific laws. The laws of classical mechanics govern the behaviour of objects in the macroscopic world, which includes everything from billiard balls to stars, while the laws of quantum mechanics govern the behaviour of the particles that make up individual atoms.
The new math is new only in that the material is introduced at a much lower level than heretofore. Thus geometry, which was and is commonly taught in the second year of high school, is now frequently introduced, in an elementary fashion, in the fourth grade-in fact, naming and recognition of the common geometric figures, the circle and the square, occurs in kindergarten. At an early stage, numbers are identified with points on a line, and the identification is used to introduce, much earlier than in the traditional curriculum, negative numbers and the arithmetic processes involving them.
The elements of set theory constitute the most basic and perhaps the most important topic of the new math. Even a kindergarten child can understand, without formal definition, the meaning of a set of red blocks, the set of fingers on the left hand, and the set of the child’s ears and eyes. The technical word set is merely a synonym for many common words that designate an aggregate of elements. The child can understand that the set of fingers on the left hand and the set on the right-hand match-that is, the elements, fingers, can be put into a one-to-one correspondence. The set of fingers on the left hand and the set of the child’s ears and eyes do not match. Some concepts that are developed by this method are counting, equality of number, more than, and less then. The ideas of union and intersection of sets and the complement of a set can be similarly developed without formal definition in the early grades. The principles and formalism of set theory are extended as the child advances; upon graduation from high school, the student’s knowledge is quite comprehensive.
The amount of new math and the particular topics taught vary from school to school. In addition to set theory and intuitive geometry, the material is usually chosen from the following topics: a development of the number systems, including methods of numeration, binary and other bases of notation, and modular arithmetic; measurement, with attention to accuracy and precision, and error study; studies of algebraic systems, including linear algebra, modern algebra, vectors, and matrices, with an axiomatically delegated approach; logic, including truth tables, the nature of proof, Venn or Euler diagrams, relations, functions, and general axiomatic; probability and statistics; linear programming; computer programming and language; and analytic geometry and calculus. Some schools present differential equations, topology, and real and complex analysis.
Cosmology, of an evolution, is the study of the general nature of the universe in space and in time-what it is now, what it was in the past and what it is likely to be in the future. Since the only forces at work between the galaxies that makes up the material universe are the forces of gravity, the cosmological problem is closely connected with the theory of gravitation, in particular with its modern version as comprised in Albert Einstein's general theory of relativity. In the frame of this theory the properties of space, time and gravitation are merged into one harmonious and elegant picture.
The basic cosmological notion of general relativity grew out of the work of great mathematicians of the 19th century. In the middle of the last century two inquisitive mathematical minds-Russian named Nikolai Lobachevski and a Hungarian named János Bolyai-discovered that the classical geometry of Euclid was not the only possible geometry: in fact, they succeeded in constructing a geometry that was fully as logical and self-consistent as the Euclidean. They began by overthrowing Euclid's axiom about parallel lines: namely, that only one parallel to a given straight line can be drawn through a point not on that line. Lobachevski and Bolyai both conceived a system of geometry in which a great number of lines parallel to a given line could be drawn through a point outside the line.
To illustrate the differences between Euclidean geometry and their non-Euclidean system considering just two dimensions are simplest-that is, the geometry of surfaces. In our schoolbooks this is known as ‘plane geometry’, because the Euclidean surface is a flat surface. Suppose, now, we examine the properties of a two-dimensional geometry constructed not on a plane surface but on a curved surface. For the system of Lobachevski and Bolyai we must take the curvature of the surface to be ‘negative’, which means that the curvature is not like that of the surface of a sphere but like that of a saddle. Now if we are to draw parallel lines or any figure (e.g., a triangle) on this surface, we must decide first of all how we will define a ‘straight line’, equivalent to the straight line of plane geometry. The most reasonable definition of a straight line in Euclidean geometry is that it is the path of the shortest distance between two points. On a curved surface the line, so defined, becomes a curved line known as a ‘geodesic’.
Considering a surface curved like a saddle, we find that, given a ‘straight’ line or geodesic, we can draw through a point outside that line a great many geodesics that will never intersect the given line, no matter how far they are extended. They are therefore parallel to it, by the definition of parallel. The possible parallels to the line fall within certain limits, indicated by the intersecting lines.
As a consequence of the overthrow of Euclid's axiom on parallel lines, many of his theorems are demolished in the new geometry. For example, the Euclidean theorem that the sum of the three angles of a triangle is 180 degrees no longer holds on a curved surface. On the saddle-shaped surface the angles of a triangle formed by three geodesics always add up to less than 180 degrees, the actual sum depending on the size of the triangle. Further, a circle on the saddle surface does not have the same properties as a circle in plane geometry. On a flat surface the circumference of a circle increases in proportion to the increase in diameter, and the area of a circle increases in proportion to the square of the increase in diameter. Still, on a saddle surface both the circumference and the area of a circle increase at faster rates than on a flat surface with increasing diameter.
After Lobachevski and Bolyai, the German mathematician Bernhard Riemann constructed another non-Euclidean geometry whose two-dimensional model is a surface of positive, rather than negative, curvature-that is, the surface of a sphere. In this case a geodesic line is simply a great circle around the sphere or a segment of such a circle, and since any two great circles must intersect at two points (the poles), there are no parallel lines at all in this geometry. Again the sum of the three angles of a triangle is not 180 degrees: in this case it is always more than 180. The circumference of a circle now increases at a rate slower than in proportion to its increase in diameter, and its area increases more slowly than the square of the diameter.
Now all this is not merely an exercise in abstract reasoning but bears directly on the geometry of the universe in which we live. Is the space of our universe ‘flat’, as Euclid assumed, or is it curved negatively (per Lobachevski and Bolyai) or curved positively (Riemann)? If we were two-dimensional creatures living in a two-dimensional universe, we could tell whether we were living on a flat or a curved surface by studying the properties of triangles and circles drawn on that surface. Similarly as three-dimensional beings living in three-dimensional space, in that we should be capably able by way of studying geometrical properties of that space, to decide what the curvature of our space is. Riemann in fact developed mathematical formulas describing the properties of various kinds of curved space in three and more dimensions. In the early years of this century Einstein conceived the idea of the universe as a curved system in four dimensions, embodying time as the fourth dimension, and he proceeded to apply Riemann's formulas to test his idea.
Einstein showed that time can be considered a fourth coordinate supplementing the three coordinates of space. He connected space and time, thus establishing a ‘space-time continuum’, by means of the speed of light as a link between time and space dimensions. However, recognizing that space and time are physically different entities, he employed the imaginary number Á, or me, to express the unit of time mathematically and make the time coordinate formally equivalent to the three coordinates of space.
In his special theory of relativity Einstein made the geometry of the time-space continuum strictly Euclidean, that is, flat. The great idea that he introduced later in his general theory was that gravitation, whose effects had been neglected in the special theory, must make it curved. He saw that the gravitational effect of the masses distributed in space and moving in time was equivalent to curvature of the four-dimensional space-time continuum. In place of the classical Newtonian statement that ‘the sun produces a field of forces that impel the earth to deviate from straight-line motion and to move in a circle around the sun’. Einstein substituted a statement to the effect that ‘the presence of the sun causes a curvature of the space-time continuum in its neighbourhood’.
The motion of an object in the space-time continuum can be represented by a curve called the object's ‘world line’. Einstein declared, in effect: ‘The world line of the earth is a geodesic trajectory in the curved four-dimensional space around the sun’. In other words, the . . . earth’s ‘world line’ . . . corresponds to the shortest four-dimensional distance between the position of the earth in January . . . and its position in October . . .
Einstein's idea of the gravitational curvature of space-time was, of course, triumphantly affirmed by the discovery of perturbations in the motion of Mercury at its closest approach to the sun and of the deflection of light rays by the sun's gravitational field. Einstein next attempted to apply the idea to the universe as a whole. Does it have a general curvature, similar to the local curvature in the sun's gravitational field? He now had to consider not a single centre of gravitational force but countless focal points in a universe full of matter concentrated in galaxies whose distribution fluctuates considerably from region to region in space. However, in the large-scale view the galaxies are spread uniformly throughout space as far out as our biggest telescopes can see, and we can justifiably ‘smooth out’ its matter to a general average (which comes to about one hydrogen atom per cubic metre). On this assumption the universe as a whole has a smooth general curvature.
Nevertheless, if the space of the universe is curved, what is the sign of this curvature? Is it positive, as in our two-dimensional analogy of the surface of a sphere, or is it negative, as in the case of a saddle surface? Since we cannot consider space alone, how is this space curvature related to time?
Analysing the pertinent mathematical equations, Einstein came to the conclusion that the curvature of space must be independent of time, i.e., that the universe as a whole must be unchanging (though it changes internally). However, he found to his surprise that there was no solution of the equations that would permit a static cosmos. To repair the situation, Einstein was forced to introduce an additional hypothesis that amounted to the assumption that a new kind of force was acting among the galaxies. This hypothetical force had to be independent of mass (being the same for an apple, the moon and the sun) and to gain in strength with increasing distance between the interacting objects (as no other forces ever do in physics).
Einstein's new force, called ‘cosmic repulsion’, allowed two mathematical models of a static universe. One solution, which was worked out by Einstein himself and became known as, Einstein's spherical universe, gave the space of the cosmos a positive curvature. Like a sphere, this universe was closed and thus had a finite volume. The space coordinates in Einstein's spherical universe were curved in the same way as the latitude or longitude coordinates on the surface of the earth. However, the time axis of the space-time continuum ran quite straight, as in the good old classical physics. This means that no cosmic event would ever recur. The two-dimensional analogy of Einstein's space-time continuum is the surface of a cylinder, with the time axis running parallel to the axis of the cylinder and the space axis perpendicular to it.
The other static solution based on the mysterious repulsion forces was discovered by the Dutch mathematician Willem de Sitter. In his model of the universe both space and time were curved. Its geometry was similar to that of a globe, with longitude serving as the space coordinate and latitude as time. Unhappily astronomical observations contradicted by both Einstein and de Sitter's static models of the universe, and they were soon abandoned.
In the year 1922 a major turning point came in the cosmological problem. A Russian mathematician, Alexander A. Friedman (from whom the author of this article learned his relativity), discovered an error in Einstein's proof for a static universe. In carrying out his proof Einstein had divided both sides of an equation by a quantity that, Friedman found, could become zero under certain circumstances. Since division by zero is not permitted in algebraic computations, the possibility of a nonstatic universe could not be excluded under the circumstances in question. Friedman showed that two nonstatic models were possible. One depiction as afforded by the efforts as drawn upon the imagination can see that the universe as expanding with time, others, by contrast, are less neuronally excited and cannot see beyond any celestial attempt for looking.
Einstein quickly recognized the importance of this discovery. In the last edition of his book The Meaning of Relativity he wrote: "The mathematician Friedman found a way out of this dilemma. He showed that having a finite density in the whole is possible, according to the field equations, (three-dimensional) space, without enlarging these field equations. Einstein remarked to me many years ago that the cosmic repulsion idea was the biggest blunder that he ever made in his entire life
Almost at the very moment that Friedman was discovering the possibility of an expanding universe by mathematical reasoning, Edwin P. Hubble at the Mount Wilson Observatory on the other side of the world found the first evidence of actual physical expansion through his telescope. He made a compilation of the distances of a number of far galaxies, whose light was shifted toward the red end of the spectrum, and it was soon found that the extent of the shift was in direct proportion to a galaxy's distance from us, as estimated by its faintness. Hubble and others interpreted the red-shift as the Doppler effect-the well-known phenomenon of lengthening of wavelengths from any radiating source that is moving rapidly away (a train whistle, a source of light or whatever). To date there has been no other reasonable explanation of the galaxies' red-shift. If the explanation is correct, it means that the galaxies are all moving away from one another with increasing velocity as they move farther apart. Thus, Friedman and Hubble laid the foundation for the theory of the expanding universe. The theory was soon developed further by a Belgian theoretical astronomer, Georges Lemaître. He proposed that our universe started from a highly compressed and extremely hot state that he called the ‘primeval atom’. (Modern physicists would prefer the term ‘primeval nucleus’.) As this matter expanded, it gradually thinned out, cooled down and reaggregated in stars and galaxies, giving rise to the highly complex structure of the universe as we now know it to be.
Not until a few years ago the theory of the expanding universe lay under the cloud of a very serious contradiction. The measurements of the speed of flight of the galaxies and their distances from us indicated that the expansion had started about 1.8 billion years ago. On the other hand, measurements of the age of ancient rocks in the earth by the clock of radioactivity (i.e., the decay of uranium to lead) showed that some of the rocks were at least three billion years old; more recent estimates based on other radioactive elements raise the age of the earth's crust to almost five billion years. Clearly a universe 1.8 billion years old could not contain five-billion-year-old rocks! Happily the contradiction has now been disposed of by Walter Baade's recent discovery that the distance yardstick (based on the periods of variable stars) was faulty and that the distances between galaxies are more than twice as great as they were thought to be. This change in distances raises the age of the universe to five billion years or more.
Friedman's solution of Einstein's cosmological equation, permits two kinds of universe. We can call one the ‘pulsating’ universe. This model says that when the universe has reached a certain maximum permissible expansion, it will begin to contract; that it will shrink until its matter has been compressed to a certain maximum density, possibly that of atomic nuclear material, which is a hundred million times denser than water; that it will then begin to expand again-and so on through the cycle ad infinitum. The other model is a ‘hyperbolic’ one: it suggests that from an infinitely thin state an eternity ago the universe contracted until it reached the maximum density, from which it rebounded to an unlimited expansion that will go on indefinitely in the future.
The question whether our universe is ‘pulsating’ or ‘hyperbolic’ should be decidable from the present rate of its expansion. The situation is analogous to the case of a rocket shot from the surface of the earth. If the velocity of the rocket is less than seven miles per second-the ‘escape velocity’-the rocket will climb only to a certain height and then fall back to the earth. (If it were completely elastic, it would bounce up again, . . . and so on.) On the other hand, a rockets shot with a velocity of more than seven miles per second will escape from the earth's gravitational field and disappeared in space. The case of the receding system of galaxies is very similar to that of an escape rocket, except that instead of just two interacting bodies: the rocket and the earth, we have an unlimited number of them escaping from one another. We find that the galaxies are fleeing from one another at seven times the velocity necessary for mutual escape.
Thus we may conclude that our universe corresponds to the ‘hyperbolic’ model, so that its present expansion will never stop. We must make one reservation. The estimate of the necessary escape velocity is based on the assumption that practically all the mass of the universe is concentrated in galaxies. If intergalactic space contained matter whose total mass was more than seven times that in the galaxies, we would have to reverse our conclusion and decide that the universe is pulsating. There has been no indication so far, however, that any matter exists in intergalactic space. It could have escaped detection only if it were in the form of pure hydrogen gas, without other gases or dust.
Is the universe finite or infinite? This resolves itself into the question: Is the curvature of space positive or negative-closed like that of a sphere, or open like that of a saddle? We can look for the answer by studying the geometrical properties of its three-dimensional space, just as we examined the properties of figures on two-dimensional surfaces. The most convenient property to investigate astronomically is the relation between the volume of a sphere and its radius.
We saw that, in the two-dimensional case, the area of a circle increases with increasing radius at a faster rate on a negatively curved surface than on a Euclidean or flat surface; and that on a positively curved surface the relative rate of increase is slower. Similarly the increase of volume is faster in negatively curved space, slower in positively curved space. In Euclidean space the volume of a sphere would increase in proportion to the cube, or third power, of the increase in radius. In negatively curved space the volume would increase faster than this, in undisputably curved space, slower. Thus if we look into space and find that the volume of successively larger spheres, as measured by a count of the galaxies within them, increases faster than the cube of the distance to the limit of the sphere (the radius), we can conclude that the space of our universe has negative curvature, and therefore is open and infinite. Similarly, if the number of galaxies increases at a rate slower than the cube of the distance, we live in a universe of positive curvature-closed and finite.
Following this idea, Hubble undertook to study the increase in number of galaxies with distance. He estimated the distances of the remote galaxies by their relative faintness: galaxies vary considerably in intrinsic brightness, but over a very large number of galaxies these variations are expected to average out. Hubble's calculations produced the conclusion that the universe is a closed system-a small universe only a few billion light-years in radius.
We know now that the scale he was using was wrong: with the new yardstick the universe would be more than twice as large as he calculated. Nevertheless, there is a more fundamental doubt about his result. The whole method is based on the assumption that the intrinsic brightness of a galaxy remains constant. What if it changes with time? We are seeing the light of the distant galaxies as it was emitted at widely different times in the past-500 million, a billion, two billion years ago. If the stars in the galaxies are burning out, the galaxies must dim as they grow older. A galaxy two billion light-years away cannot be put on the same distance scale with a galaxy 500 million light-years away unless we take into account the fact that we are seeing the nearer galaxy at an older, and less bright, age. The remote galaxy is farther away than a mere comparison of the luminosity of the two would suggest.
When a correction is made for the assumed decline in brightness with age, the more distant galaxies are spread out to farther distances than Hubble assumed. In fact, the calculations of volume are nonetheless drastically that we may have to reverse the conclusion about the curvature of space. We are not sure, because we do not yet know enough about the evolution of galaxies. Even so, if we find that galaxies wane in intrinsic brightness by only a few per cent in a billion years, we will have to conclude that space is curved negatively and the universe is infinite.
Effectively there is another line of reasoning which supports the side of infinity. Our universe seems to be hyperbolic and ever-expanding. Mathematical solutions of fundamental cosmological equations indicate that such a universe is open and infinite.
We have reviewed the questions that dominated the thinking of cosmologists during the first half of this century: the conception of a four-dimensional space-time continuum, of curved space, of an expanding universe and of a cosmos that is either finite or infinite. Now we must consider the major present issue in cosmology: Is the universe in truth evolving, or is it in a steady state of equilibrium that has always existed and will go on through eternity? Most cosmologists take the evolutionary view. All the same, in 1951 a group at the University of Cambridge, whose chief official representative has been Fred Hoyle, advanced the steady-state idea. Essentially their theory is that the universe is infinite in space and time that it has neither a beginning nor an end, that the density of its matter remains constant, that new matter is steadily being created in space at a rate that exactly compensates for the thinning of matter by expansion, that as a consequence new galaxies are continually being born, and that the galaxies of the universe therefore range in age from mere youngsters to veterans of 5, 10, 20 and more billions of years. In my opinion this theory must be considered very questionable because of the simple fact (apart from other reasons) that the galaxies in our neighbourhood all seem to be of the same age as our own Milky Way. However, the issue is many-sided and fundamental, and can be settled only by extended study of the universe as far as we can observe it . . . Thus coming to summarize the evolutionary theory.
We assume that the universe started from a very dense state of matter. In the early stages of its expansion, radiant energy was dominant over the mass of matter. We can measure energy and matter on a common scale by means of the well-known equation E=mc2, which says that the energy equivalent of matter is the mass of the matter multiplied by the square of the velocity of light. Energy can be translated into mass, conversely, by dividing the energy quantity by c2. Thus, we can speak of the ‘mass density’ of energy. Now at the beginning the mass density of the radiant energy was incomparably greater than the density of the matter in the universe. Yet in an expanding system the density of radiant energy decreases faster than does the density of matter. The former thins out as the fourth power of the distance of expansion: as the radius of the system doubles, the density of radiant energy drops to one sixteenth. The density of matter declines as the third power; a doubling of the radius means an eightfold increase in volume, or eightfold decrease in density.
Assuming that the universe at the beginning was under absolute rule by radiant energy, we can calculate that the temperature of the universe was 250 million degrees when it was one hour old, dropped to 6,000 degrees (the present temperature of our sun's surface) when it was 200,000 years old and had fallen to about 100 degrees below the freezing point of water when the universe reached its 250-millionth birthday.
This particular birthday was a crucial one in the life of the universe. It was the point at which the density of ordinary matter became greater than the mass density of radiant energy, because of the more rapid fall of the latter. The switch from the reign of radiation to the reign of matter profoundly changed matter's behaviours. During the eons of its subjugation to the will of radiant energy (i.e., light), it must have been spread uniformly through space in the form of thin gas. Nevertheless, as soon as matter became gravitationally more important than the radiant energy, it began to acquire a more interesting character. James Jeans, in his classic studies of the physics of such a situation, proved half a century ago that a gravitating gas filling a very large volume is bound to break up into individual ‘gas balls’, the size of which is determined by the density and the temperature of the gas. Thus in the year 250,000,000 A.B.E. (after the beginning of expansion), when matter was freed from the dictatorship of radiant energy, the gas broke up into giant gas clouds, slowly drifting apart as the universe continued to expand. Applying Jeans's mathematical formula for the process to the gas filling the universe at that time, in that these primordial balls of gas would have had just about the mass that the galaxies of stars possess today. They were then only ‘proto galaxies’-cold, dark and chaotic. However, their gas soon condensed into stars and formed the galaxies as we see them now.
A central question in this picture of the evolutionary universe is the problem of accounting for the formation of the varied kinds of matter composing it, i.e., the chemical elements . . . Its belief is that at the start matter was composed simply of protons, neutrons and electrons. After five minutes the universe must have cooled enough to permit the aggregation of protons and neutrons into larger units, from deuterons (one neutron and one proton) up to the heaviest elements. This process must have ended after about thirty minutes, for by that time the temperature of the expanding universe must have dropped below the threshold of thermonuclear reactions among light elements, and the neutrons must have been used up in element-building or been converted to protons.
To many, the statement that the present chemical constitution of our universe was decided in half an hour five billion years ago will sound nonsensical. However, consider a spot of ground on the atomic proving ground in Nevada where an atomic bomb was exploded three years ago. Within one microsecond the nuclear reactions generated by the bomb produced a variety of fission products. Today, 100 million-million microseconds later, the site is still ‘hot’ with the surviving fission products. The ratio of one microsecond to three years is the same as the ratio of half an hour to five billion years! If we can accept a time ratio of this order in the one case, why not in the other?
The late Enrico Fermi and Anthony L. Turkevich at the Institute for Nuclear Studies of the University of Chicago undertook a detailed study of thermonuclear reactions such as must have taken place during the first half hour of the universe's expansion. They concluded that the reactions would have produced about equal amounts of hydrogen and helium, making up 99 per cent of the total material, and about 1 per cent of deuterium. We know that hydrogen and helium do in fact make up about 99 per cent of the matter of the universe. This leaves us with the problem of building the heavier elements. Hold to opinion, that some of them were built by capture of neutrons. However, since the absence of any stable nucleus of atomic weight five makes it improbable that the heavier elements could have been produced in the first half hour in the abundances now observed, and, yet agreeing that the lion's share of the heavy elements may have been formed later in the hot interiors of stars.
All the theories-of the origin, age, extent, composition and nature of the universe-are becoming more subject to test by new instruments and new techniques . . . Nevertheless, we must not forget that the estimate of distances of the galaxies is still founded on the debatable assumption that the brightness of galaxies does not change with time. If galaxies diminish in brightness as they age, the calculations cannot be depended upon. Thus the question whether evolution is or is not taking place in the galaxies is of crucial importance at the present stage of our outlook on the universe.
In addition certain branches of physical science focus on energy and its large-scale effects. Thermodynamics is the study of heat and the effects of converting heat into other kinds of energy. This branch of physics has a host of highly practical applications because heat is often used to power machines. Physicists also investigate electrical energy and energy that are carried in electromagnetic waves. These include radio waves, light rays, and X-rays-forms of energy that are closely related and that all obey the same set of rules. Chemistry is the study of the composition of matter and the way different substances interact-subjects that involve physics on an atomic scale. In physical chemistry, chemists study the way physical laws govern chemical change, while in other branches of chemistry the focus is on particular chemicals themselves. For example, inorganic chemistry investigates substances found in the nonliving world and organic chemistry investigates carbon-based substances. Until the 19th century, these two areas of chemistry were thought to be separate and distinct, but today chemists routinely produce organic chemicals from inorganic raw materials. Organic chemists have learned how to synthesize many substances that are found in nature, together with hundreds of thousands that are not, such as plastics and pesticides. Many organic compounds, such as reserpine, a drug used to treat hypertension, cost less to produce by synthesizing from inorganic raw materials than to isolate from natural sources. Many synthetic medicinal compounds can be modified to make them more effective than their natural counterparts, with fewer harmful side effects.
The branch of chemistry known as biochemistry deals solely with substances found in living things. It investigates the chemical reactions that organisms use to obtain energy and the reactions up which they use to build themselves. Increasingly, this field of chemistry has become concerned not simply with chemical reactions themselves but also with how the shape of molecules influences the way they work. The result is the new field of molecular biology, one of the fastest-growing sciences today.
Physical scientists also study matter elsewhere in the universe, including the planets and stars. Astronomy is the science of the heavens usually, while astrophysics is a branch of astronomy that investigates the physical and chemical nature of stars and other objects. Astronomy deals largely with the universe as it appears today, but a related science called cosmology looks back in time to answer the greatest scientific questions of all: how the universe began and how it came to be as it is today
The life sciences include all those areas of study that deal with living things. Biology is the general study of the origin, development, structure, function, evolution, and distribution of living things. Biology may be divided into botany, the study of plants; zoology, the study of animals; and microbiology, the study of the microscopic organisms, such as bacteria, viruses, and fungi. Many single-celled organisms play important roles in life processes and thus are important to more complex forms of life, including plants and animals.
Genetics is the branch of biology that studies the way in which characteristics are transmitted from an organism to its offspring. In the latter half of the 20th century, new advances made it easier to study and manipulate genes at the molecular level, enabling scientists to catalogue all the genes finds in each cell of the human body. Exobiology, a new and still speculative field, is the study of possible extraterrestrial life. Although Earth remains the only place known to support life, many believe that it is only a matter of time before scientists discover life elsewhere in the universe.
While exobiology is one of the newest life sciences, anatomy is one of the oldest. It is the study of plant and animal structures, carried out by dissection or by using powerful imaging techniques. Gross anatomy deals with structures that are large enough to see, while microscopic anatomy deals with much smaller structures, down to the level of individual cells.
Physiology explores how living things’ work. Physiologists study processes such as cellular respiration and muscle contraction, as well as the systems that keep these processes under control. Their work helps to answer questions about one of the key characteristics of life, the fact that most living things maintain a steady internal state when the environment around them constantly changes.
Together, anatomy and physiology form two of the most important disciplines in medicine, the science of treating injury and human disease. General medical practitioners have to be familiar with human biology as a whole, but medical science also includes a host of clinical specialties. They include sciences such as cardiology, urology, and oncology, which investigate particular organs and disorders, and pathology, the general study of disease and the changes that it causes in the human body.
As well as working with individual organisms, life scientists also investigate the way living things interact. The study of these interactions, known as ecology, has become a key area of study in the life sciences as scientists become increasingly concerned about the disrupting effects of human activities on the environment.
The social sciences explore human society past and present, and the way human beings behave. They include sociology, which investigates the way society is structured and how it functions, as well as psychology, which is the study of individual behaviour and the mind. Social psychology draws on research in both these fields. It examines the way society influence’s people's behaviour and attitudes.
Another social science, anthropology, looks at humans as a species and examines all the characteristics that make us what we are. These include not only how people relate to each other but also how they interact with the world around them, both now and in the past. As part of this work, anthropologists often carry out long-term studies of particular groups of people in different parts of the world. This kind of research helps to identify characteristics that all human beings share. That there are those that are the products of some non-regional culture, in that have been taught by others in sharing their knowledge as given up from generation to generation.
The social sciences also include political science, law, and economics, which are products of human society. Although far removed from the world of the physical sciences, all these fields can be studied in a scientific way. Political science and law are uniquely human concepts, but economics has some surprisingly close parallels with ecology. This is because the laws that govern resource use, productivity, and efficiency do not operate only in the human world, with its stock markets and global corporations, but in the nonhuman world as well in technology, scientific knowledge is put to practical ends. This knowledge comes chiefly from mathematics and the physical sciences, and it is used in designing machinery, materials, and industrial processes. Overall, this work is known as engineering, a word dating back to the early days of the Industrial Revolution, when an ‘engine’ was any kind of machine.
Engineering has many branches, calling for a wide variety of different skills. For example, aeronautical engineers need expertise in the science of fluid flow, because aeroplanes fly through air, which is a fluid. Using wind tunnels and computer models, aeronautical engineers strive to minimize the air resistance generated by an aeroplane, while at the same time maintaining a sufficient amount of lift. Marine engineers also need detailed knowledge of how fluids behave, particularly when designing submarines that have to withstand extra stresses when they dive deep below the water’s surface. In civil engineering, stress calculations ensure that structures such as dams and office towers will not collapse, particularly if they are in earthquake zones. In computing, engineering takes two forms: hardware design and software design. Hardware design refers to the physical design of computer equipment (hardware). Software design is carried out by programmers who analyse complex operations, reducing them to a series of small steps written in a language recognized by computers.
In recent years, a completely new field of technology has developed from advances in the life sciences. Known as biotechnology, it involves such varied activities as genetic engineering, the manipulation of genetic material of cells or organisms, and cloning, the formation of genetically uniform cells, plants, or animals. Although still in its infancy, many scientists believe that biotechnology will play a major role in many fields, including food production, waste disposal, and medicine. Science exists because humans have a natural curiosity and an ability to organize and record things. Curiosity is a characteristic shown by many other animals, but organizing and recording knowledge is a skill demonstrated by humans alone.
During prehistoric times, humans recorded information in a rudimentary way. They made paintings on the walls of caves, and they also carved numerical records on bones or stones. They may also have used other ways of recording numerical figures, such as making knots in leather cords, but because these records were perishable, no traces of them remain. Even so, with the invention of writing about 6,000 years ago, a new and much more flexible system of recording knowledge appeared.
The earliest writers were the people of Mesopotamia, who lived in a part of present-day Iraq. Initially they used a pictographic script, inscribing tallies and lifelike symbols on tablets of clay. With the passage of time, these symbols gradually developed into cuneiform, a much more stylized script composed of wedge-shaped marks.
Because clay is durable, many of these ancient tablets still survive. They show that when writing first appeared. The Mesopotamians already had a basic knowledge of mathematics, astronomy, and chemistry, and that they used symptoms to identify common diseases. During the following 2,000 years, as Mesopotamian culture became increasingly sophisticated, mathematics in particular became a flourishing science. Knowledge accumulated rapidly, and by 1000 Bc the earliest private libraries had appeared.
Southwest of Mesopotamia, in the Nile Valley of northeastern Africa, the ancient Egyptians developed their own form of a pictographic script, writing on papyrus, or inscribing text in stone. Written records from 1500 Bc. shows that, like the Mesopotamians, the Egyptians had a detailed knowledge of diseases. They were also keen astronomers and skilled mathematicians-a fact demonstrated by the almost perfect symmetry of the pyramids and by other remarkable structures they built.
For the peoples of Mesopotamia and ancient Egypt, knowledge was recorded mainly for practical needs. For example, astronomical observations enabled the development of early calendars, which helped in organizing the farming year. Yet in ancient Greece, often recognized as the birthplace of Western science, a new scientific enquiry began. Here, philosophers sought knowledge largely for its own sake.
Thales of Miletus were one of the first Greek philosophers to seek natural causes for natural phenomena. He travelled widely throughout Egypt and the Middle East and became famous for predicting a solar eclipse that occurred in 585 Bc. At a time when people regarded eclipses as ominous, inexplicable, and frightening events, his prediction marked the start of rationalism, a belief that the universe can be explained by reason alone. Rationalism remains the hallmark of science to this day.
Thales and his successors speculated about the nature of matter and of Earth itself. Thales himself believed that Earth was a flat disk floating on water, but the followers of Pythagoras, one of ancient Greece's most celebrated mathematicians, believed that Earth was spherical. These followers also thought that Earth moved in a circular orbit-not around the Sun but around a central fire. Although flawed and widely disputed, this bold suggestion marked an important development in scientific thought: the idea that Earth might not be, after all, the centre of the universe. At the other end of the spectrum of scientific thought, the Greek philosopher Leucippus and his student Democritus of Abdera proposed that all matter be made up of indivisible atoms, more than 2,000 years before the idea became a part of modern science.
As well as investigating natural phenomena, ancient Greek philosophers also studied the nature of reasoning. At the two great schools of Greek philosophy in Athens-the Academy, founded by Plato, and the Lyceum, founded by Plato's pupil Aristotle-students learned how to reason in a structured way using logic. The methods taught at these schools included induction, which involve taking particular cases and using them to draw general conclusions, and deduction, the process of correctly inferring new facts from something already known.
In the two centuries that followed Aristotle's death in 322 Bc, Greek philosophers made remarkable progress in a number of fields. By comparing the Sun's height above the horizon in two different places, the mathematician, astronomer, and geographer Eratosthenes calculated Earth's circumference, producing the figure of an accurate overlay within one percent. Another celebrated Greek mathematician, Archimedes, laid the foundations of mechanics. He also pioneered the science of hydrostatics, the study of the behaviour of fluids at rest. In the life sciences, Theophrastus founded the science of botany, providing detailed and vivid descriptions of a wide variety of plant species as well as investigating the germination process in seeds.
By the 1st century Bc, Roman power was growing and Greek influence had begun to wane. During this period, the Egyptian geographer and astronomer Ptolemy charted the known planets and stars, putting Earth firmly at the centre of the universe, and Galen, a physician of Greek origin, wrote important works on anatomy and physiology. Although skilled soldiers, lawyers, engineers, and administrators, the Romans had little interest in basic science. As a result, scientific growth made little advancement in the days of the Roman Empire. In Athens, the Lyceum and Academy were closed down in AD. 529, bringing the first flowering of rationalism to an end.
For more than nine centuries, from about ad 500 to 1400, Western Europe made only a minor contribution to scientific thought. European philosophers became preoccupied with alchemy, a secretive and mystical pseudoscience that held out the illusory promise of turning inferior metals into gold. Alchemy did lead to some discoveries, such as sulfuric acid, which was first described in the early 1300's, but elsewhere, particularly in China and the Arab world, much more significant progress in the sciences was made.
Chinese science developed in isolation from Europe, and followed a different pattern. Unlike the Greeks, who prized knowledge as an end, the Chinese excelled at turning scientific discoveries to practical ends. The list of their technological achievements is dazzling: it includes the compass, invented in about AD. 270; wood-block printing, developed around 700, and gunpowder and movable type, both invented around the year 1000. The Chinese were also capable mathematicians and excellent astronomers. In mathematics, they calculated the value of π (pi) to within seven decimal places by the year 600, while in astronomy, one of their most celebrated observations was that of the supernova, or stellar explosion, that took place in the Crab Nebula in 1054. China was also the source of the world's oldest portable star map, dating from about 940 Bc.
The Islamic world, which in medieval times extended as far west as Spain, also produced many scientific breakthroughs. The Arab mathematician Muhammad al-Khwarizmi introduced Hindu-Arabic numerals to Europe many centuries after they had been devised in southern Asia. Unlike the numerals used by the Romans, Hindu-Arabic numerals include zero, a mathematical device unknown in Europe at the time. The value of Hindu-Arabic numerals depends on their place: in the number 300, for example, the numeral three is worth ten times as much as in thirty. Al-Khwarizmi also wrote on algebra (it derived from the Arab word al-jabr), and his name survives in the word algorithm, a concept of great importance in modern computing.
In astronomy, Arab observers charted the heavens, giving many of the brightest stars the names we use today, such as Aldebaran, Altair, and Deneb. Arab scientists also explored chemistry, developing methods to manufacture metallic alloys and test the quality and purity of metals. As in mathematics and astronomy, Arab chemists left their mark in some of the names they used-alkali and alchemy, for example, are both words of Arabic origin. Arab scientists also played a part in developing physics. One of the most famous Egyptian physicists, Alhazen, published a book that dealt with the principles of lenses, mirrors, and other devices used in optics. In this work, he rejected the then-popular idea that eyes give out light rays. Instead, he correctly deduced that eyes work when light rays enter the eye from outside.
In Europe, historians often attribute the rebirth of science to a political event-the capture of Constantinople (now Istanbul) by the Turks in 1453. At the time, Constantinople was the capital of the Byzantine Empire and a major seat of learning. Its downfall led to an exodus of Greek scholars to the West. In the period that followed, many scientific works, including those originally from the Arab world, were translated into European languages. Through the invention of the movable type printing press by Johannes Gutenberg around 1450, copies of these texts became widely available.
The Black Death, a recurring outbreak of bubonic plague that began in 1347, disrupted the progress of science in Europe for more than two centuries. However, in 1543 two books were published that had a profound impact on scientific progress. One was De Corporis Humani Fabrica (On the Structure of the Human Body, seven volumes, 1543), by the Belgian anatomist Andreas Vesalius. Vesalius studied anatomy in Italy, and his masterpiece, which was illustrated by superb woodcuts, corrected errors and misunderstandings about the body before which had persisted since the time of Galen more than 1,300 years. Unlike Islamic physicians, whose religion prohibited them from dissecting human cadavers, Vesalius investigated the human body in minute detail. As a result, he set new standards in anatomical science, creating a reference work of unique and lasting value.
The other book of great significance published in 1543 was De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres), written by the Polish astronomer. In it, Copernicus rejected the idea that Earth was the centre of the universe, as proposed by Ptolemy in the 1st century Bc. Instead, he set out to prove that Earth, together with the other planets, follows orbits around the Sun. Other astronomers opposed Copernicus's ideas, and more ominously, so did the Roman Catholic Church. In the early 1600's, the church placed the book on a list of forbidden works, where it remained for more than two centuries. Despite this ban and despite the book's inaccuracies (for instance, Copernicus believed that Earth's orbit was circular rather than elliptical), De Revolutionibus remained a momentous achievement. It also marked the start of a conflict between science and religion that has dogged Western thought ever since
In the first decade of the 17th century, the invention of the telescope provided independent evidence to support Copernicus's views. Italian physicist and astronomer Galileo Galilei used the new device to remarkable effect. He became the first person to observe satellites circling Jupiter, the first to make detailed drawings of the surface of the Moon, and the first to see how Venus waxes and wanes as it circles the Sun.
These observations of Venus helped to convince Galileo that Copernicus’s Sun-entered view of the universe had been correct, but he fully understood the danger of supporting such heretical ideas. His Dialogue on the Two Chief World Systems, Ptolemaic and Copernican, published in 1632, was carefully crafted to avoid controversy. Even so, he was summoned before the Inquisition (tribunal established by the pope for judging heretics) the following year and, under threat of torture, forced to recant.
Nicolaus Copernicus (1473-1543), the first developed heliocentric theory of the Universes in the modern era presented in De Revolutioniv bus Coelestium, published in the year of Copernicus’s death. The system is entirely mathematical, in the sense of predicting the observed position of celestial bodies on te basis of an underlying geometry, without exploring the mechanics of celestial motion. Its mathematical and scientific superiority over the Ptolemaic system was not as direct as poplar history suggests: Copernicus’s system adhered to circular planetary motion and let the planets run on forty-eight epicycles and eccentrics. It was not until the work of Kepler and Galileo that the system became markedly simpler than Ptolemaic astronomy.
The publication of Nicolaus Copernicus's De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres) in 1543 is traditionally considered the inauguration of the scientific revolution. Ironically, Copernicus had no intention of introducing radical ideas into cosmology. His aim was only to restore the purity of ancient Greek astronomy by eliminating novelties introduced by Ptolemy. With such an aim in mind he modelled his own book, which would turn astronomy upside down, on Ptolemy's Almagest. At the core of the Copernican system, as with that of Aristarchus before him, is the concept of the stationary Sun at the centre of the universe, and the revolution of the planets, Earth included, around the Sun. The Earth was ascribed, in addition to an annual revolution around the Sun, a daily rotation around its axis.
Copernicus's greatest achievement is his legacy. By introducing mathematical reasoning into cosmology, he dealt a severe blow to Aristotelian commonsense physics. His concept of an Earth in motion launched the notion of the Earth as a planet. His explanation that he had been unable to detect stellar parallax because of the enormous distance of the sphere of the fixed stars opened the way for future speculation about an infinite universe. Nevertheless, Copernicus still clung to many traditional features of Aristotelian cosmology. He continued to advocate the entrenched view of the universe as a closed world and to see the motion of the planets as uniform and circular. Thus, in evaluating Copernicus's legacy, it should be noted that he set the stage for far more daring speculations than he himself could make. The heavy metaphysical underpinning of Kepler's laws, combined with an obscure style and a demanding mathematics, caused most contemporaries to ignore his discoveries. Even his Italian contemporary Galileo Galilei, who corresponded with Kepler and possessed his books, never referred to the three laws. Instead, Galileo provided the two important elements missing from Kepler's work: a new science of dynamics that could be employed in an explanation of planetary motion, and a staggering new body of astronomical observations. The observations were made possible by the invention of the telescope in Holland c.1608 and by Galileo's ability to improve on this instrument without having ever seen the original. Thus equipped, he turned his telescope skyward, and saw some spectacular sights.
The results of his discoveries were immediately published in the Sidereus nuncius (The Starry Messenger) of 1610. Galileo observed that the Moon was very similar to the Earth, with mountains, valleys, and oceans, and not at all that perfect, smooth spherical body it was claimed to be. He also discovered four moons orbiting Jupiter. As for the Milky Way, instead of being a stream of light, it was, alternatively a large aggregate of stars. Later observations resulted in the discovery of sunspots, the phases of Venus, and that strange phenomenon that would later be designated as the rings of Saturn.
Having announced these sensational astronomical discoveries which reinforced his conviction of the reality of the heliocentric theory-Galileo resumed his earlier studies of motion. He now attempted to construct a comprehensive new science of mechanics necessary in a Copernican world, and the results of his labours were published in Italian in two epoch
- making books: Dialogue Concerning the Two Chief World Systems (1632) and Discourses and Mathematical Demonstrations Concerning the Two New Sciences (1638). His studies of projectiles and free-falling bodies brought him very close to the full formulation of the laws of inertia and acceleration (the first two laws of Isaac Newton). Galileo's legacy includes both the modern notion of ‘laws of nature’ and the idea of mathematics as nature's true language. He contributed to the mathematization of nature and the geometrization of space, as well as to the mechanical philosophy that would dominate the 17th and 18th centuries. Perhaps most important, it is largely due to Galileo that experiments and observations serve as the cornerstone of scientific reasoning.
Today, Galileo is remembered equally well because of his conflict with the Roman Catholic church. His uncompromising advocacy of Copernicanism after 1610 was responsible, in part, for the placement of Copernicus's De Revolutionibus on the Index of Forbidden Books in 1616. At the same time, Galileo was warned not to teach or defend Copernicanism in public. The election of Galileo's friend Maffeo Barbering as Pope Urban VIII in 1624 filled Galileo with the hope that such a verdict could be revoked. With perhaps some unwarranted optimism, Galileo set to work to complete his Dialogue (1632). However, Galileo underestimated the power of the enemies he had made during the previous two decades, particularly some Jesuits who had been the target of his acerbic tongue. The outcome was that Galileo was summoned to Rome and there forced to abjure, on his knees, the views he had expressed in his book. Ever since, Galileo has been portrayed as a victim of a repressive church and a martyr in the cause of freedom of thought; as such, he has become a powerful symbol.
Despite his passionate advocacy of Copernicanism and his fundamental work in mechanics, Galileo continued to accept the age-old views that planetary orbits were circular and the cosmos an enclosed world. These beliefs, as well as a reluctance rigorously to apply mathematics to astronomy as he had previously applied it to terrestrial mechanics, prevented him from arriving at the correct law of inertia. Thus, it remained for Isaac Newton to unite heaven and Earth in his immense intellectual achievement, the Philosophiae Naturalis principia mathematica (Mathematical Principles of Natural Philosophy), which was published in 1687. The first book of the Principia contained Newton's three laws of motion. The first expounds the law of inertia: everybody persists in a state of rest or uniform motion in a straight line unless compelled to change such a state by an impressing force. The second is the law of acceleration, according to which the change of motion of a body is proportional to the force acting upon it and takes place in the direction of the straight line along which that force is impressed. The third, and most original, law ascribes to every action an opposite and equal reaction. These laws governing terrestrial motion were extended to include celestial motion in book three of the Principia, where Newton formulated his most famous law, the law of gravitation: everybody in the universe attracts any other body with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
The Principia is deservedly considered one of the greatest scientific masterpieces of all time. Nevertheless, in 1704, Newton published his second great work, the Opticks, in which he formulated his corpuscular theory of light and his theory of colours. In later editions Newton appended a series of ‘queries’ concerning various related topics in natural philosophy. These speculative, and sometimes metaphysical, statements on such issues as light, heat, ether, and matter became most productive during the 18th century, when the book and the experimental method it propagated became immensely popular.
The 17th century French scientist and mathematician René Descartes was also one of the most influential thinkers in Western philosophy. Descartes stressed the importance of skepticism in thought and proposed the idea that existence had a dual nature: one physical, the other mental. The latter concept, known as Cartesian dualism, continues to engage philosophers today. This passage from Discourse on Method (first published in his Philosophical Essays in 1637) contains a summary of his thesis, which includes the celebrated phrase “I think, therefore I am.”
Then examining attentively what I was, and seeing that I could pretend that I had no body and that there was no world or place that I [was] in, but that I could not, for all that, pretend that I did not exist, and that, on the contrary, from the very fact that I thought of doubting the truth of other things, it followed very evidently and very conveniently that I existed; while, on the other hand, if I had only ceased to think, although all the rest of what I had ever imagined had been true, I would have had no reason to believe that I existed; I thereby concluded that I was a substance, of which the whole essence or nature consists in thinking, and which, in order to exist, needs no place and depends on no material thing; so that this ‘I’, which is to say, the mind, by which I am what I am, is distinct entirely from the body, and even that knowing is easier than the body, and moreover that even if the body were not, it would not cease to be all that it is.
It is, nonetheless, as considered overall of what is needed for a proposition to be true and certain; for, I had morally justified, in finding of one that so happens that I knew it to be so. I thought too, that I had morally justified by reason alone, in that to know of what is of this necessitates a narrative coherence as availed to a set-order of governing principles. Having marked and noted that there is nothing in at all that in this, I think, therefore I am, which assures me that I am speaking the truth, except that I see very clearly that in order to think one must exist, I judged that I could take it to be a general rule that the things we conceive very clearly and very distinctly is nevertheless some difficulty in being able to recognize for certain that are the things we see distinctly.
Following this, reflecting on the fact that I had doubts, and that consequently my being was not perfect, for I saw clearly that it was a greater perfection to know than to doubt, I decided to inquire from what place I had learned to think of some thing perfect than myself; and I clearly recognized that this must have been from some nature that was in fact perfect. As for the notions I had of several other things outside myself, such as the sky, the earth, light, heat and a thousand others, I had not the same concern to know their source, because, seeing nothing in them that seemed to make them superior to me. I could believe that, if they were true, they were dependencies of my nature, in as much as it. One perfection; and, if they were not, that I held them from nothing, that is to say that they were in me because of an imperfection in my nature. Nevertheless, I could not make the same judgement concerning the idea of a being perfect than myself; for to hold it from nothing was something manifestly impossible; and because it is no less contradictory that the perfect should proceed from and depend on the less perfect, than it is that something should emerge out of nothing, I could not hold it from myself; with the result that it remained that it must have been put into me by a being whose nature was truly perfect than mine and which even had in it all the perfection of which I could have any idea, which is to say, in a word, which was God. To which I added that, since I knew some perfections that I did not have, I was not the only being that existed (I will freely use here, with your permission, the terms of the School) but that there must be another perfect, upon whom I depended, and from whom I had acquired all I had; for, if I had been alone and independent of all other, so as to have had from myself this small portion of perfection that I had by participation in the perfection of God, I could have given myself, by the same reason, all the remainder of perfection that I knew myself to lack, and thus to be myself infinite, eternal, immutable, omniscient, all powerful, and finally to have all the perfections that I could observe to be in God. For, consequentially upon the reasoning by which I had proved the existence of God, in order to understand the nature of God as far as my own nature was capable of doing, I had only to consider, concerning all the things of which I found in myself some idea, whether it was a perfection or not to have them: and I was assured that none of those that indicated some imperfection was in him, but that all the others were. So I saw that doubt, inconstancy, sadness and similar things could not be in him, seeing that I myself would have been very pleased to be free from them. Then, further, I had ideas of many sensible and bodily things; for even supposing that I was dreaming, and that everything I saw or imagined was false, I could not, nevertheless, deny that the ideas were really in my thoughts. However, because I had already recognized in myself very clearly that intelligent nature is distinct from the corporeal, considering that all composition is evidence of dependency, and that dependency is manifestly a defect, I thence judged that it could not be a perfection in God to be composed of these two natures, and that, consequently, he was not so composed, but that, if there were any bodies in the world or any intelligence or other natures that were not wholly perfect, their existence must depend on his power, in such a way that they could not subsist without him for a single instant.
I set out after that to seek other truths; and turning to the object of the geometers [geometry], which I conceived as a continuous body, or a space extended indefinitely in length, width and height or depth, divisible into various parts, which could have various figures and sizes and be moved or transposed in all sorts of ways-for the geometers take all that to be in the object of their study-I went through some of their simplest proofs. Having observed that the great certainty that everyone attributes to them is based only on the fact that they are clearly conceived according to the rule I spoke of earlier, I noticed also that they had nothing at all in them that might assure me of the existence of their object. Thus, for example, I very well perceived that, supposing a triangle to be given, its three angles must be equal to two right-angles, but I saw nothing, for all that, which assured me that any such triangle existed in the world, whereas regressing to the examination of the idea I had of a perfect Being. In that of its finding it was found that existence was comprised in the idea in the same way that the equality of the three angles of a triangle to two right angles is comprised in the idea of a triangle or, as in the idea of a sphere, the fact that all its parts are equidistant from its centre, or even more obviously so; and that consequently it is at least as certain that God, who is this perfect Being, is, or exists, as any geometric demonstration can be.
The impact of the Newtonian accomplishment was enormous. Newton's two great books resulted in the establishment of two traditions that, though often mutually exclusive, nevertheless permeated into every area of science. The first was the mathematical and reductionist tradition of the Principia, which, like René Descartes's mechanical philosophy, propagated a rational, well-regulated image of the universe. The second was the experimental tradition of the Opticks, in a measure less demanding than the mathematical tradition and, owing to the speculative and suggestive queries appended to the Opticks, highly applicable to chemistry, biology, and the other new scientific disciplines that began to flourish in the 18th century. This is not to imply that everyone in the scientific establishment was, or would be, a Newtonian. Newtonianism had its share of detractors. Instead, the Newtonian achievement was so great, and its applicability to other disciplines so strong, that although Newtonian science could be argued against, it could not be ignored. In fact, in the physical sciences an initial reaction against universal gravitation occurred. For many, the concept of action at a distance seemed to hark back to those occult qualities with which the mechanical philosophy of the 17th century had done away. By the second half of the 18th century, however, universal gravitation would be proved correct, thanks to the work of Leonhard Euler, A. C. Clairaut, and Pierre Simon de LaPlace, the last of whom announced the stability of the solar system in his masterpiece Celestial Mechanics (1799-1825).
Newton's influence was not confined to the domain of the natural sciences. The philosophes of the 18th-century Enlightenment sought to apply scientific methods to the study of human society. To them, the empiricist philosopher John Locke was the first person to attempt this. They believed that in his Essay on Human Understanding (1690) Locke did for the human mind what Newton had done for the physical world. Although Locke's psychology and epistemology were to come under increasing attack as the 18th century advanced, other thinkers such as Adam Smith, David Hume, and Abbé de Condillac would aspire to become the Newtons of the mind or the moral realm. These confident, optimistic men of the Enlightenment argued that there must exist universal human laws that transcend differences of human behaviour and the variety of social and cultural institutions. Labouring under such an assumption, they sought to uncover these laws and apply them to the new society about which they hoped to bring.
As the 18th century progressed, the optimism of the philosophes waned and a reaction began to set in. Its first manifestation occurred in the religious realm. The mechanistic interpretation of the world-shared by Newton and Descartes -had, in the hands of the philosophes, led to materialism and atheism. Thus, by mid-century the stage was set for a revivalist movement, which took the form of Methodism in England and pietism in Germany. By the end of the century the romantic reaction had begun. Fuelled in part by religious revivalism, the romantics attacked the extreme rationalism of the Enlightenment, the impersonalization of the mechanistic universe, and the contemptuous attitude of "mathematicians" toward imagination, emotions, and religion.
The romantic reaction, however, was not anti-scientific; its adherents rejected a specific type of the mathematical science, not the entire enterprise. In fact, the romantic reaction, particularly in Germany, would give rise to a creative movement-the Naturphilosophie -that in turn would be crucial for the development of the biological and life sciences in the 19th century, and would nourish the metaphysical foundation necessary for the emergence of the concepts of energy, forces, and conservation.
Thus and so, in classical physics, external reality consisted of inert and inanimate matter moving in accordance with wholly deterministic natural laws, and collections of discrete atomized parts constituted wholes. Classical physics was also premised, however, on a dualistic conception of reality as consisting of abstract disembodied ideas existing in a domain separate from and superior to sensible objects and movements. The motion that the material world experienced by the senses was inferior to the immaterial world experiences by mind or spirit has been blamed for frustrating the progress of physics up too at least the time of Galileo. Nevertheless, in one very important respect it also made the fist scientific revolution possible. Copernicus, Galileo, Kepler and Newton firmly believed that the immaterial geometrical mathematical ides that inform physical reality had a prior existence in the mind of God and that doing physics was a form of communion with these ideas.
Even though instruction at Cambridge was still dominated by the philosophy of Aristotle, some freedom of study was permitted in the student's third year. Newton immersed himself in the new mechanical philosophy of Descartes, Gassendi, and Boyle; in the new algebra and analytical geometry of Vieta, Descartes, and Wallis; and in the mechanics and Copernican astronomy of Galileo. At this stage Newton showed no great talent. His scientific genius emerged suddenly when the plague closed the University in the summer of 1665 and he had to return to Lincolnshire. There, within eighteen months he began revolutionary advances in mathematics, optics, physics, and astronomy.
During the plague years Newton laid the foundation for elementary differential and integral Calculus, several years before its independent discovery by the German philosopher and mathematician Leibniz. The ‘method of fluxions’, as he termed it, was based on his crucial insight that the integration of a function (or finding the area under its curve) is merely the inverse procedure to differentiating it (or finding the slope of the curve at any point). Taking differentiation as the basic operation, Newton produced simple analytical methods that unified a host of disparate techniques previously developed on a piecemeal basis to deal with such problems as finding areas, tangents, the lengths of curves, and their maxima and minima. Even though Newton could not fully justify his methods -rigorous logical foundations for the calculus were not developed until the 19th century-he receives the credit for developing a powerful tool of problem solving and analysis in pure mathematics and physics. Isaac Barrow, a Fellow of Trinity College and Lucasian Professor of Mathematics in the University, was so impressed by Newton's achievement that when he resigned his chair in 1669 to devote himself to theology, he recommended that the 27-year-old Newton take his place.
Newton's initial lectures as Lucasian Professor dealt with optics, including his remarkable discoveries made during the plague years. He had reached the revolutionary conclusion that white light is not a simple, homogeneous entity, as natural philosophers since Aristotle had believed. When he passed a thin beam of sunlight through a glass prism, he noted the oblong spectrum of colours-red, yellow, green, blue, violet -that formed on the wall opposite. Newton showed that the spectrum was too long to be explained by the accepted theory of the bending (or refraction) of light by dense media. The old theory said that all rays of white light striking the prism at the same angle would be equally refracted. Newton argued that white light is really a mixture of many different types of rays, that the different types of rays are refracted at different angles, and that each different type of ray is responsible for producing a given spectral colour. A so-called crucial experiment confirmed the theory. Newton selected out of the spectrum a narrow band of light of one colour. He sent it through a second prism and observed that no further elongation occurred. All the selected rays of one colour were refracted at the same angle.
These discoveries led Newton to the logical, but erroneous, conclusion that telescopes using refracting lenses could never overcome the distortions of chromatic dispersion. He therefore proposed and constructed a reflecting telescope, the first of its kind, and the prototype of the largest modern optical telescopes. In 1671 he donated an improved version to the Royal Society of London, the foremost scientific society of the day. As a consequence, he was elected a fellow of the society in 1672. Later that year Newton published his first scientific paper in the Philosophical Transactions of the society. It dealt with the new theory of light and colour and is one of the earliest examples of the short research paper.
Newton's paper was well received, but two leading natural philosophers, Robert Hooke and Christian Huygens rejected Newton's naive claim that his theory was simply derived with certainty from experiments. In particular they objected to what they took to be Newton's attempt to prove by experiment alone that light consists in the motion of small particles, or corpuscles, rather than in the transmission of waves or pulses, as they both believed. Although Newton's subsequent denial of the use of hypotheses was not convincing, his ideas about scientific method won universal assent, along with his corpuscular theory, which reigned until the wave theory was revived in the early 19th century.
The debate soured Newton's relations with Hooke. Newton withdrew from public scientific discussion for about a decade after 1675, devoting himself to chemical and alchemical researches. He delayed the publication of a full account of his optical researches until after the death of Hooke in 1703. Newton's Opticks appeared the following year. It dealt with the theory of light and colour and with Newton's investigations of the colours of thin sheets, of ‘Newton's rings’, and of the phenomenon of diffraction of light. To explain some of his observations he had to graft elements of a wave theory of light onto his basically corpuscular theory. q
Newton's greatest achievement was his work in physics and celestial mechanics, which culminated in the theory of universal gravitation. Even though Newton also began this research in the plague years, the story that he discovered universal gravitation in 1666 while watching an apple fall from a tree in his garden is a myth. By 1666, Newton had formulated early versions of his three Laws of motion. He had also discovered the law stating the centrifugal force (or force away from the centre) of a body moving uniformly in a circular path. However, he still believed that the earth's gravity and the motions of the planets might be caused by the action of whirlpools, or vortices, of small corpuscles, as Descartes had claimed. Moreover, although he knew the law of centrifugal force, he did not have a correct understanding of the mechanics of circular motion. He thought of circular motion as the result of a balance between two forces. One centrifugal, the other centripetal (toward the centre)-than as the result of one force, a centripetal force, which constantly deflects the body away from its inertial path in a straight line.
Newton's great insight of 1666 was to imagine that the Earth's gravity extended to the Moon, counterbalancing its centrifugal force. From his law of centrifugal force and Kepler's third law of planetary motion, Newton deduced that the centrifugal (and hence centripetal) forces of the Moon or of any planet must decrease as the inverse square of its distance from the centre of its motion. For example, if the distance is doubled, the force becomes one-fourth as much; if distance is trebled, the force becomes one-ninth as much. This theory agreed with Newton's data to within about 11%.
In 1679, Newton returned to his study of celestial mechanics when his adversary Hooke drew him into a discussion of the problem of orbital motion. Hooke is credited with suggesting to Newton that circular motion arises from the centripetal deflection of inertially moving bodies. Hooke further conjectured that since the planets move in ellipses with the Sun at one focus (Kepler's first law), the centripetal force drawing them to the Sun should vary as the inverse square of their distances from it. Hooke could not prove this theory mathematically, although he boasted that he could. Not to be shown up by his rival, Newton applied his mathematical talents to proving Hooke's conjecture. He showed that if a body obeys Kepler's second law (which states that the line joining a planet to the sun sweeps out equal areas in equal times), then the body is being acted upon by a centripetal force. This discovery revealed for the first time the physical significance of Kepler's second law. Given this discovery, Newton succeeded in showing that a body moving in an elliptical path and attracted to one focus must truly be drawn by a force that varies as the inverse square of the distance. Later even these results were set aside by Newton.
In 1684 the young astronomer Edmond Halley, tired of Hooke's fruitless boasting, asked Newton whether he could prove Hooke's conjecture and to his surprise was told that Newton had solved the problem a full five years before but had now mislaid the paper. At Halley's constant urging Newton reproduced the proofs and expanded them into a paper on the laws of motion and problems of orbital mechanics. Finally Halley persuaded Newton to compose a full-length treatment of his new physics and its application to astronomy. After eighteen months of sustained effort, Newton published (1687) the Philosophiae Naturalis principia Mathematica (The Mathematical Principles of Natural Philosophy), or Principia, as it is universally known.
By common consent the Principia is the greatest scientific book ever written. Within the framework of an infinite, homogeneous, three-dimensional, empty space and a uniformly and eternally flowing ‘absolute’ time, Newton fully analysed the motion of bodies in resisting and nonresisting media under the action of centripetal forces. The results were applied to orbiting bodies, projectiles, pendula, and free-fall near the Earth. He further demonstrated that the planets were attracted toward the Sun by a force varying as the inverse square of the distance and generalized that all heavenly bodies mutually attract one another. By further generalization, he reached his law of universal gravitation: every piece of matter attracts every other piece with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.
Given the law of gravitation and the laws of motion, Newton could explain a wide range of hitherto disparate phenomena such as the eccentric orbits of comets, the causes of the tides and their major variations, the precession of the Earth's axis, and the perturbation of the motion of the Moon by the gravity of the Sun. Newton's one general law of nature and one system of mechanics reduced to order most of the known problems of astronomy and terrestrial physics. The work of Galileo, Copernicus, and Kepler was united and transformed into one coherent scientific theory. The new Copernican world-picture finally had a firm physical basis.
Because Newton repeatedly used the term ‘attraction’ in the Principia, mechanical philosophers attacked him for reintroducing into science the idea that mere matter could act at a distance upon other matter. Newton replied that he had only intended to show the existence of gravitational attraction and to discover its mathematical law, not to inquire into its cause. He no more than his critics believed that brute matter could act at a distance. Having rejected the Cartesian vortices, he reverted in the early 1700s to the idea that some material medium, or ether, caused gravity. However, Newton's ether was no longer a Cartesian-type ether acting solely by impacts among particles. The ether had to be extremely rare so it would not obstruct the motions of the planets, and yet very elastic or springy so it could push large masses toward one another. Newton postulated that the new ether consisted of particles endowed with very powerful short-range repulsive forces. His unreconciled ideas on forces and ether deeply influenced later natural philosophers in the 18th century when they turned to the phenomena of chemistry, electricity and magnetism, and physiology.
With the publication of the Principia, Newton was recognized as the leading natural philosopher of the age, but his creative career was effectively over. After suffering a nervous breakdown in 1693, he retired from research to seek a government position in London. In 1696 he became Warden of the Royal Mint and in 1699 its Master, an extremely lucrative position. He oversaw the great English recoinage of the 1690s and pursued counterfeiters with ferocity. In 1703 he was elected president of the Royal Society and was reelected each year until his death. He was knighted (1708) by Queen Anne, the first scientist to be so honoured for his work.
As any overt appeal to metaphysics became unfashionable, the science of mechanics was increasingly regarded, says Ivor Leclerc, as ‘an autonomous science,’ and any alleged role of God as ‘deus ex machina’. At the beginning of the nineteenth century, Pierre-Simon LaPlace, along with a number of other great French mathematicians and, advanced the view that the science of mechanics constituted a complex view of nature. Since this science, by observing its epistemology, had revealed itself to be the fundamental science, the hypothesis of God as, they concluded unnecessary.
Pierre de Simon LaPlace (1749-1827) is recognized for eliminating not only the theological component of classical physics but the ‘entire metaphysical component’ as well. The epistemology of science requires, had that we proceeded by inductive generalisations from observed facts to hypotheses that are ‘tested by observed conformity of the phenomena.’ What was unique out LaPlace’s view of hypotheses as insistence that we cannot attribute reality to them. Although concepts like force, mass, notion, cause, and laws are obviously present in classical physics, they exist in LaPlace’s view only as quantities. Physics is concerned, he argued, with quantities that we associate as a matter of convenience with concepts, and the truths abut nature are only quantities.
The seventeenth-century view of physics s a philosophy of nature or as natural philosophy was displaced by the view of physics as an autonomous science that was: The science of nature. This view, which was premised on the doctrine e of positivism, promised to subsume all of the nature with a mathematical analysis of entities in motion and claimed that the true understanding of nature was revealed only in the mathematical descriptions. Since the doctrine of positivism, assumed that the knowledge we call physics resides only in the mathematical formalisms of physical theory, it disallows the prospect that the vision of physical reality revealed in physical theory can have any other meaning. In the history of science, the irony is that positivism, which was intended to banish metaphysical concerns from the domain of science, served to perpetuate a seventeenth-century metaphysical assumption about the relationship between physical reality and physical theory.
So, then, the decision was motivated by our conviction that our discoveries have more potential to transform our conception of the ‘way thing are’ than any previous discovery in the history of science, as these implications of discovery extend well beyond the domain of the physical sciences, and the best efforts of large numbers of thoughtfully convincing in others than I will be required to understand them.
In fewer contentious areas, European scientists made rapid progress on many fronts in the 17th century. Galileo himself investigated the laws governing falling objects, and discovered that the duration of a pendulum's swing is constant for any given length. He explored the possibility of using this to control a clock, an idea that his son put into practice in 1641. Two years later another Italian, mathematician and physicist Evangelists Torricelli, made the first barometer. In doing so he discovered atmospheric pressure and produced the first artificial vacuum known to science. In 1650 German physicist Otto von Guericke invented the air pump. He is best remembered for carrying out a demonstration of the effects of atmospheric pressure. Von Guericke joined two large, hollow bronze hemispheres, and then pumped out the air within them to form a vacuum. To illustrate the strength of the vacuum, von Guericke showed how two teams of eight horses pulling in opposite directions could not separate the hemispheres. Yet the hemispheres fell apart as soon as air was let in.
Throughout the 17th century major advances occurred in the life sciences, including the discovery of the circulatory system by the English physician William Harvey and the discovery of microorganisms by the Dutch microscope maker Antoni van Leeuwenhoek. In England, Robert Boyle established modern chemistry as a full-fledged science, while in France, philosopher and scientist René Descartes made numerous discoveries in mathematics, as well as advancing the case for rationalism in scientific research.
However, the century's greatest achievements came in 1665, when the English physicist and mathematician Isaac Newton fled from Cambridge to his rural birthplace in Woolsthorpe to escape an epidemic of the plague. There, in the course of a single year, he made a series of extraordinary breakthroughs, including new theories about the nature of light and gravitation and the development of calculus. Newton is perhaps best known for his proof that the force of gravity extends throughout the universe and that all objects attract each other with a precisely defined and predictable force. Gravity holds the Moon in its orbit around the Earth and is the principal cause of the Earth’s tides. These discoveries revolutionized how people viewed the universe and they marked the birth of modern science.
Newton’s work demonstrated that nature was governed by basic rules that could be identified using the scientific method. This new approach to nature and discovery liberated 18th-century scientists from passively accepting the wisdom of ancient writings or religious authorities that had never been tested by experiment. In what became known as the Age of Reason, or the Age of Enlightenment, scientists in the 18th century began to apply rational thought actively, careful observation, and experimentation to solve a variety of problems.
Advances in the life sciences saw the gradual erosion of the theory of spontaneous generation, a long-held notion that life could spring from nonliving matter. It also brought the beginning of scientific classification, pioneered by the Swedish naturalist Carolus Linnaeus, who classified close to 12,000 living plants and animals into a systematic arrangement.
By 1700 the first steam engine had been built. Improvements in the telescope enabled German-born British astronomer Sir William Herschel to discover the planet Uranus in 1781. Throughout the 18th century science began to play an increasing role in everyday life. New manufacturing processes revolutionized the way that products were made, heralding the Industrial Revolution. In An Inquiry Into the Nature and Causes of the Wealth of Nations, published in 1776, British economist Adam Smith stressed the advantages of division of labour and advocated the use of machinery to increase production. He urged governments to allow individuals to compete within a free market in order to produce fair prices and maximum social benefit. Smith’s work for the first time gave economics the stature of an independent subject of study and his theories greatly influenced the course of economic thought for more than a century.
With knowledge in all branches of science accumulating rapidly, scientists began to specialize in particular fields. Specialization did not necessarily mean that discoveries were specializing as well: From the 19th century onward, research began to uncover principles that unite the universe as a whole.
In chemistry, one of these discoveries was a conceptual one: that all matter is made of atoms. Originally debated in ancient Greece, atomic theory was revived in a modern form by the English chemist John Dalton in 1803. Dalton provided clear and convincing chemical proof that such particles exist. He discovered that each atom has a characteristic mass and that atoms remain unchanged when they combine with other atoms to form compound substances. Dalton used atomic theory to explain why substances always combine in fixed proportions-a field of study known as quantitative chemistry. In 1869 Russian chemist Dmitry Mendeleyev used Dalton’s discoveries about atoms and their behaviour to draw up his periodic table of the elements.
Other 19th-century discoveries in chemistry included the world's first synthetic fertilizer, manufactured in England in 1842. In 1846 German chemist Christian Schoenbein accidentally developed the powerful and unstable explosive nitrocellulose. The discovery occurred after he had spilled a mixture of nitric and sulfuric acids and then mopped it up with a cotton apron. After the apron had been hung up to dry, it exploded. He later learned that the cellulose in the cotton apron combined with the acids to form a highly flammable explosive.
In 1828 the German chemist Friedrich Wöhler showed that making carbon-containing was possible, organic compounds from inorganic ingredients, a breakthrough that opened an entirely new field of research. By the end of the 19th century, hundreds of organic compounds had been synthesized, including mauve, magenta, and other synthetic dyes, as well as aspirin, still one of the world's most useful drugs.
In physics, the 19th century is remembered chiefly for research into electricity and magnetism, which were pioneered by physicists such as Michael Faraday and James Clerk Maxwell of Great Britain. In 1821 Faraday demonstrated that a moving magnet could set an electric current flowing in a conductor. This experiment and others he carried as a process, led to the development of electric motors and generators. While Faraday’s genius lay in discovery by experiment, Maxwell produced theoretical breakthroughs of even greater note. Maxwell's development of the electromagnetic theory of light took many years. It began with the paper ‘On Faraday's Lines of Force’ (1855–1856), in which Maxwell built on the ideas of British physicist Michael Faraday. Faraday explained that electric and magnetic effects result from lines of forces that surround conductors and magnets. Maxwell drew an analogy between the behaviour of the lines of force and the flow of a liquid, deriving equations that represented electric and magnetic effects. The next step toward Maxwell’s electromagnetic theory was the publication of the paper, On Physical Lines of Force (1861-1862). Here Maxwell developed a model for the medium that could carry electric and magnetic effects. He devised a hypothetical medium that consisted of a fluid in which magnetic effects created whirlpool-like structures. These whirlpools were separated by cells created by electric effects, so the combination of magnetic and electric effects formed a honeycomb pattern.
Maxwell could explain all known effects of electromagnetism by considering how the motion of the whirlpools, or vortices, and cells could produce magnetic and electric effects. He showed that the lines of force behave like the structures in the hypothetical fluid. Maxwell went further, considering what would happen if the fluid could change density, or be elastic. The movement of a charge would set up a disturbance in an elastic medium, forming waves that would move through the medium. The speed of these waves would be equal to the ratio of the value for an electric current measured in electrostatic units to the value of the same current measured in electromagnetic units. German physicists Friedrich Kohlrausch and Wilhelm Weber had calculated this ratio and found it the same as the speed of light. Maxwell inferred that light consists of waves in the same medium that causes electric and magnetic phenomena.
Maxwell found supporting evidence for this inference in work he did on defining basic electrical and magnetic quantities in terms of mass, length, and time. In the paper, On the Elementary Regulations of Electric Quantities (1863), he wrote that the ratio of the two definitions of any quantity based on electric and magnetic forces is always equal to the velocity of light. He considered that light must consist of electromagnetic waves but first needed to prove this by abandoning the vortex analogy and developing a mathematical system. He achieved this in ‘A Dynamical Theory of the Electromagnetic Field’ (1864), in which he developed the fundamental equations that describe the electromagnetic field. These equations showed that light is propagated in two waves, one magnetic and the other electric, which vibrate perpendicular to each other and perpendicular to the direction in which they are moving (like a wave travelling along a string). Maxwell first published this solution in Note on the Electromagnetic Theory of Light (1868) and summed up all of his work on electricity and magnetism in Treatise on Electricity and Magnetism in 1873.
The treatise also suggested that a whole family of electromagnetic radiation must exist, of which visible light was only one part. In 1888 German physicist Heinrich Hertz made the sensational discovery of radio waves, a form of electromagnetic radiation with wavelengths too long for our eyes to see, confirming Maxwell’s ideas. Unfortunately, Maxwell did not live long enough to see this vindication of his work. He also did not live to see the ether (the medium in which light waves were said to be propagated) disproved with the classic experiments of German-born American physicist Albert Michelson and American chemist Edward Morley in 1881 and 1887. Maxwell had suggested an experiment much like the Michelson-Morley experiment in the last year of his life. Although Maxwell believed the ether existed, his equations were not dependent on its existence, and so remained valid.
Maxwell's other major contribution to physics was to provide a mathematical basis for the kinetic theory of gases, which explains that gases behave as they do because they are composed of particles in constant motion. Maxwell built on the achievements of German physicist Rudolf Clausius, who in 1857 and 1858 had shown that a gas must consist of molecules in constant motion colliding with each other and with the walls of their container. Clausius developed the idea of the mean free path, which is the average distance that a molecule travels between collisions.
Maxwell's development of the kinetic theory of gases was stimulated by his success in the similar problem of Saturn's rings. It dates from 1860, when he used a statistical treatment to express the wide range of velocities (speeds and the directions of the speeds) that the molecules in a quantity of gas must inevitably possess. He arrived at a formula to express the distribution of velocity in gas molecules, relating it to temperature. He showed that gases store heat in the motion of their molecules, so the molecules in a gas will speed up as the gasses temperature increases. Maxwell then applied his theory with some success to viscosity (how much a gas resists movement), diffusion (how gas molecules move from an area of higher concentration to an area of lower concentration), and other properties of gases that depend on the nature of the molecules’ motion.
Maxwell's kinetic theory did not fully explain heat conduction (how heat travels through a gas). Austrian physicist Ludwig Boltzmann modified Maxwell’s theory in 1868, resulting in the Maxwell-Boltzmann distribution law, showing the number of particles (n) having an energy (E) in a system of particles in thermal equilibrium. It has the form:
n = n0 exp(-E/kT),
Where n0 is the number of particles having the lowest energy, ‘k’ the Boltzmann constant, and ‘T’ the thermodynamic temperature.
If the particles can only have certain fixed energies, such as the energy levels of atoms, the formula gives the number (Ei) above the ground state energy. In certain cases several distinct states may have the same energy and the formula then becomes:
ni = gin0 exp(-Ki/kT),
Where (g)I is the statistical weight of the level of energy ‘Ei’,
i.e., the number of states having energy Ei. The distribution of energies obtained by the formula is called a Boltzmann distribution.
Both Maxwell’ s thermodynamic relational equations and the Boltzmann formulation to a contributorial successive succession of refinements of kinetic theory, and it proved fully applicable to all properties of gases. It also led Maxwell to an accurate estimate of the size of molecules and to a method of separating gases in a centrifuge. The kinetic theory was derived using statistics, so it also revised opinions on the validity of the second law of thermodynamics, which states that heat cannot flow from a colder to a hotter body of its own accord. In the case of two connected containers of gases at the same temperature, it is statistically possible for the molecules to diffuse so that the faster-moving molecules all concentrate in one container while the slower molecules gather in the other, making the first container hotter and the second colder. Maxwell conceived this hypothesis, which is known as Maxwell's demon. Although this event is very unlikely, it is possible, and the second law is therefore not absolute, but highly probable.
These sources provide additional information on James Maxwell Clerk: Maxwell is generally considered the greatest theoretical physicist of the 1800s. He combined a rigorous mathematical ability with great insight, which enabled him to make brilliant advances in the two most important areas of physics at that time. In building on Faraday's work to discover the electromagnetic nature of light, Maxwell not only explained electromagnetism but also paved the way for the discovery and application of the whole spectrum of electromagnetic radiation that has characterized modern physics. Physicists now know that this spectrum also includes radio, infrared, ultraviolet, and X-ray waves, to name a few. In developing the kinetic theory of gases, Maxwell gave the final proof that the nature of heat resides in the motion of molecules.
With Maxwell's famous equations, as devised in 1864, uses mathematics to explain the interactions between electric and magnetic fields. His work demonstrated the principles behind electromagnetic waves created when electric and magnetic fields oscillate simultaneously. Maxwell realized that light was a form of electromagnetic energy, but he also thought that the complete electromagnetic spectrum must include many other forms of waves as well.
With the discovery of radio waves by German physicist Heinrich Hertz in 1888 and X-rays by German physicist Wilhelm Roentgen in 1895, Maxwell’s ideas were proved correct. In 1897 British physicist Sir Joseph J. Thomson discovered the electron, a subatomic particle with a negative charge. This discovery countered the long-held notion that atoms were the basic unit of matter.
As in chemistry, these 19th-century discoveries in physics proved to have immense practical value. No one was more adept at harnessing them than American physicist and prolific inventor Thomas Edison. Working from his laboratories in Menlo Park, New Jersey, Edison devised the carbon-granule microphone in 1877, which greatly improved the recently invented telephone. He also invented the phonograph, the electric light bulb, several kinds of batteries, and the electric metre. Edison was granted more than 1,000 patents for electrical devices, a phenomenal feat for a man who had no formal schooling.
In the earth sciences, the 19th century was a time of controversy, with scientists debating Earth's age. Estimated ranges may be as far as from less than 100,000 years to several hundred million years. In astronomy, greatly improved optical instruments enabled important discoveries to be made. The first observation of an asteroid, Ceres, took place in 1801. Astronomers had long noticed that Uranus exhibited an unusual orbit. French astronomer Urbain Jean Joseph Leverrier predicted that another planet nearby caused Uranus’s odd orbit. Using mathematical calculations, he narrowed down where such a planet would be located in the sky. In 1846, with the help of German astronomer Johann Galle, Leverrier discovered Neptune. The Irish astronomer William Parsons, the third Earl of Rosse, became the first person to see the spiral form of galaxies beyond our own solar system. He did this with the Leviathan, a 183-cm. (72-in.) reflecting telescopes, built on the grounds of his estate in Parsonstown (now Birr), Ireland, in the 1840s. His observations were hampered by Ireland's damp and cloudy climate, but his gigantic telescope remained the world's largest for more than 70 years.
In the 19th century the study of microorganisms became increasingly important, particularly after French biologist Louis Pasteur revolutionized medicine by correctly deducing that some microorganisms are involved in disease. In the 1880's Pasteur devised methods of immunizing people against diseases by deliberately treating them with weakened forms of the disease-causing organisms themselves. Pasteur’s vaccine against rabies was a milestone in the field of immunization, one of the most effective forms of preventive medicine the world has yet seen. In the area of industrial science, Pasteur invented the process of pasteurization to help prevent the spread of disease through milk and other foods.
Pasteur’s work on fermentation and spontaneous generation had considerable implications for medicine, because he believed that the origin and development of disease are analogous to the origin and process of fermentation. That is, disease arises from germs attacking the body from outside, just as unwanted microorganisms invade milk and cause fermentation. This concept, called the germ theory of disease, was strongly debated by physicians and scientists around the world. One of the main arguments against it was the contention that the role germs played during the course of disease was secondary and unimportant; the notion that tiny organisms could kill vastly larger ones seemed ridiculous to many people. Pasteur’s studies convinced him that he was right, however, and in the course of his career he extended the germ theory to explain the causes of many diseases.
Pasteur also determined the natural history of anthrax, a fatal disease of cattle. He proved that anthrax is caused by a particular bacillus and suggested that animals could be given anthrax in a mild form by vaccinating them with attenuated (weakened) bacilli, thus providing immunity from potentially fatal attacks. In order to prove his theory, Pasteur began by inoculating twenty-five sheep; a few days later he inoculated these and twenty-five more sheep with an especially strong inoculant, and he left ten sheep untreated. He predicted that the second twenty-five sheep would all perish and concluded the experiment dramatically by showing, to a sceptical crowd, the carcasses of the twenty-five sheep lying side by side.
Pasteur spent the rest of his life working on the causes of various diseases, including septicaemia, cholera, diphtheria, fowl cholera, tuberculosis, and smallpox-and their prevention by means of vaccination. He is best known for his investigations concerning the prevention of rabies, otherwise known in humans as hydrophobia. After experimenting with the saliva of animals suffering from this disease, Pasteur concluded that the disease rests in the nerve centres of the body; when an extract from the spinal column of a rabid dog was injected into the bodies of healthy animals, symptoms of rabies were produced. By studying the tissues of infected animals, particularly rabbits, Pasteur was able to develop an attenuated form of the virus that could be used for inoculation.
In 1885, a young boy and his mother arrived at Pasteur’s laboratory; the boy had been bitten badly by a rabid dog, and Pasteur was urged to treat him with his new method. At the end of the treatment, which lasted ten days, the boy was being inoculated with the most potent rabies virus known; he recovered and remained healthy. Since that time, thousands of people have been saved from rabies by this treatment.
Pasteur’s research on rabies resulted, in 1888, in the founding of a special institute in Paris for the treatment of the disease. This became known as the Instituted Pasteur, and it was directed by Pasteur himself until he died. (The institute still flourishes and is one of the most important centres in the world for the study of infectious diseases and other subjects related to microorganisms, including molecular genetics.) By the time of his death in Saint-Cloud on September 28, 1895, Pasteur had long since become a national hero and had been honoured in many ways. He was given a state funeral at the Cathedral of Nôtre Dame, and his body was placed in a permanent crypt in his institute.
Also during the 19th century, the Austrian monk Gregor Mendel laid the foundations of genetics, although his work, published in 1866, was not recognized until after the century had closed. Nevertheless, the British scientist Charles Darwin towers above all other scientists of the 19th century. His publication of On the Origin of Species in 1859 marked a major turning point for both biology and human thought. His theory of evolution by natural selection (independently and simultaneously developed by British naturalist Alfred Russel Wallace) initiated a violent controversy that until it has not subsided. Particularly controversial was Darwin’s theory that humans resulted from a long process of biological evolution from apelike ancestors. The greatest opposition to Darwin’s ideas came from those who believed that the Bible was an exact and literal statement of the origin of the world and of humans. Although the public initially castigated Darwin’s ideas, by the late 1800s most biologists had accepted that evolution occurred, although not all agreed on the mechanism, known as natural selection, that Darwin proposed.
In the 20th century, scientists achieved spectacular advances in the fields of genetics, medicine, social sciences, technology, and physics.
At the beginning of the 20th century, the life sciences entered a period of rapid progress. Mendel's work in genetics was rediscovered in 1900, and by 1910 biologists had become convinced that genes are located in chromosomes, the threadlike structures that contain proteins and deoxyribonucleic acid (DNA). During the 1940's American biochemists discovered that DNA taken from one kind of bacterium could influence the characteristics of another. From these experiments, DNA is clearly the chemical that makes up genes and thus the key to heredity.
After American biochemist James Watson and British biophysicist Francis Crick established the structure of DNA in 1953, geneticists became able to understand heredity in chemical terms. Since then, progress in this field has been astounding. Scientists have identified the complete genome, or genetic catalogue, of the human body. In many cases, scientists now know how individual genes become activated and what affects they have in the human body. Genes can now be transferred from one species to another, sidestepping the normal processes of heredity and creating hybrid organisms that are unknown in the natural world.
At the turn of the 20th century, Dutch physician Christian Eijkman showed that disease can be caused not only by microorganisms but by a dietary deficiency of certain substances now called vitamins. In 1909 German bacteriologist Paul Ehrlich introduced the world's first bactericide, a chemical designed to kill specific kinds of bacteria without killing the patient's cells as well. Following the discovery of penicillin in 1928 by British bacteriologist Sir Alexander Fleming, antibiotics joined medicine’s chemical armoury, making the fight against bacterial infection almost a routine matter. Antibiotics cannot act against viruses, but vaccines have been used to great effect to prevent some of the deadliest viral diseases. Smallpox, once a worldwide killer, was completely eradicated by the late 1970's, and in the United States the number of polio cases dropped from 38,000 in the 1950's to less than ten a year by the 21st century. By the middle of the 20th century scientists believed they were well on the way to treating, preventing, or eradicating many of the most deadly infectious diseases that had plagued humankind for centuries. Nevertheless, by the 1980's the medical community’s confidence in its ability to control infectious diseases had been shaken by the emergence of new types of disease-causing microorganisms. New cases of tuberculosis developed, caused by bacteria strains that were resistant to antibiotics. New, deadly infections for which there was no known cure also appeared, including the viruses that cause haemorrhagic fever and the human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome.
In other fields of medicine, the diagnosis of disease has been revolutionized by the use of new imaging techniques, including magnetic resonance imaging and computed tomography. Scientists were also on the verge of success in curing some diseases using gene therapy, in which the insertion of normal or genetically an altered gene into a patient’s cells replaces nonfunctional or missing genes.
Improved drugs and new tools have made surgical operations that were once considered impossible now routine. For instance, drugs that suppress the immune system enable the transplant of organs or tissues with a reduced risk of rejection Endoscopy permits the diagnosis and surgical treatment of a wide variety of ailments using minimally invasive surgery. Advances in high-speed fiberoptic connections permit surgery on a patient using robotic instruments controlled by surgeons at another location. Known as ‘telemedicine’, this form of medicine makes it possible for skilled physicians to treat patients in remote locations or places that lack medical help.
In the 20th century the social sciences emerged from relative obscurity to become prominent fields of research. Austrian physician Sigmund Freud founded the practice of psychoanalysis, creating a revolution in psychology that led him to be called the ‘Copernicus of the mind’. In 1948 the American biologist Alfred Kinsey published Sexual Behaviour in the Human Male, which proved to be one of the best-selling scientific works of all time. Although criticized for his methodology and conclusions, Kinsey succeeded in making human sexuality an acceptable subject for scientific research.
The 20th century also brought dramatic discoveries in the field of anthropology, with new fossil finds helping to piece together the story of human evolution. A completely new and surprising source of anthropological information became available from studies of the DNA in mitochondria, cell structures that provide energy to fuel the cell’s activities. Mitochondrial DNA has been used to track certain genetic diseases and to trace the ancestry of a variety of organisms, including humans.
In the field of communications, Italian electrical engineer Guglielmo Marconi sent his first radio signal across the Atlantic Ocean in 1901. American inventor Lee De Forest invented the triode, or vacuum tube, in 1906. The triode eventually became a key component in nearly all early radio, radar, television, and computer systems. In 1920 Scottish engineer John Logie Baird developed the Baird Televisor, a primitive television that provided the first transmission of a recognizable moving image. In the 1920's and 1930's American electronic engineer Vladimir Kosma Zworykin significantly improved the television’s picture and reception. In 1935 British physicist Sir Robert Watson-Watt used reflected radio waves to locate aircraft in flight. Radar signals have since been reflected from the Moon, planets, and stars to learn their distance from Earth and to track their movements.
In 1947 American physicists John Bardeen, Walter Brattain, and William Shockley invented the transistor, an electronic device used to control or amplify an electrical current. Transistors are much smaller, far less expensive, require less power to operate, and are considerably more reliable than triodes. Since their first commercial use in hearing aids in 1952, transistors have replaced triodes in virtually all applications.
During the 1950's and early 1960's minicomputers were developed using transistors rather than triodes. Earlier computers, such as the electronic numerical integrator and computer (ENIAC), first introduced in 1946 by American physicist John W. Mauchly and American electrical engineer John Presper Eckert, Jr., used as many as 18,000 triodes and filled a large room. However, the transistor initiated a trend toward microminiaturization, in which individual electronic circuits can be reduced to microscopic size. This drastically reduced the computer's size, cost, and power requirements and eventually enabled the development of electronic circuits with processing speeds measured in billionths of a second
Further miniaturization led in 1971 to the first microprocessor-a computer on a chip. When combined with other specialized chips, the microprocessor becomes the central arithmetic and logic unit of a computer smaller than a portable typewriter. With their small size and a price less than that of a used car, today’s personal computers are many times more powerful than the physically huge, multimillion-dollar computers of the 1950's. Once used only by large businesses, computers are now used by professionals, small retailers, and students to complete a wide variety of everyday tasks, such as keeping data on clients, tracking budgets, and writing school reports. People also use computers to understand each other with worldwide communications networks, such as the Internet and the World Wide Web, to send and receive E-mail, to shop, or to find information on just about any subject.
During the early 1950's public interest in space exploration developed. The focal event that opened the space age was the International Geophysical Year from July 1957 to December 1958, during which hundreds of scientists around the world coordinated their efforts to measure the Earth’s near-space environment. As part of this study, both the United States and the Soviet Union announced that they would launch artificial satellites into orbit for nonmilitary space activities.
When the Soviet Union launched the first Sputnik satellite in 1957, the feat spurred the United States to intensify its own space exploration efforts. In 1958 the National Aeronautics and Space Administration (NASA) was founded for the purpose of developing human spaceflight. Throughout the 1960's NASA experienced its greatest growth. Among its achievements, NASA designed, manufactured, tested, and eventually used the Saturn rocket and the Apollo spacecraft for the first manned landing on the Moon in 1969. In the 1960's and 1970's, NASA also developed the first robotic space probes to explore the planet’s Mercury, Venus, and Mars. The success of the Mariner probes paved the way for the unmanned exploration of the outer planets in Earth’s solar system.
In the 1970's through 1990's, NASA focussed its space exploration efforts on a reusable space shuttle, which was first deployed in 1981. In 1998 the space shuttle, along with its Russian counterpart known as Soyuz, became the workhorses that enabled the construction of the International Space Station.
In 1900 the German physicist Max Planck proposed the then sensational idea that energy be not divisible but is always given off in set amounts, or quanta. Five years later, German-born American physicist Albert Einstein successfully used quanta to explain the photoelectric effect, which is the release of electrons when metals are bombarded by light. This, together with Einstein's special and general theories of relativity, challenged some of the most fundamental assumptions of the Newtonian era.
Unlike the laws of classical physics, quantum theory deals with events that occur on the smallest of scales. Quantum theory explains how subatomic particles form atoms, and how atoms interact when they combine to form chemical compounds. Quantum theory deals with a world where the attributes of any single particle can never be completely known-an idea known as the uncertainty principle, put forward by the German physicist Werner Heisenberg in 1927, whereby, the principle, that the product of the uncertainty in measured value of a component of momentum (pχ) and the uncertainty in the corresponding co-ordinates of (χ) is of the equivalent set-order of magnitude, as the Planck constant. In its most precise form:
Δp2 x Δχ ≥ h/4π
Where Δχ represents the root-mean-square value of the uncertainty. For mot purposes one can assume:
Δpχ x Δχ = h/2π
The principle can be derived exactly from quantum mechanics, a physical theory that grew out of Planck’s quantum theory and deals with the mechanics of atomic and related systems in terms of quantities that an be measured mathematical forms, including ‘wave mechanics’ (Schrödinger) and ‘matrix mechanics’ (Born and Heisenberg), all of which are equivalent.
Nonetheless, it is most easily understood as a consequence of the fact that any measurement of a system mist disturbs the system under investigation, with a resulting lack of precision in measurement. For example, if seeing an electron was possible and thus measures its position, photons would have to be reflected from the electron. If a single photon could be used and detected with a microscope, the collision between the electron and photon would change the electron’s momentum, as to its effectuality Compton Effect as a result to wavelengths of the photon is increased by an amount Δλ, whereby:
Δλ = (2h/m0c) sin2 ½ φ.
This is the Compton equation, h is the Planck constant, m0 the rest mass of the particle, c the speed of light, and φ the angle between the directions of the incident and scattered photon. The quantity h/m0c is known as the Compton wavelength, symbol: λC, to which for an electron is equal to 0.002 43 nm.
A similar relationship applies to the determination of energy and time, thus:
ΔE x Δt ≥ h/4π.
The effects of the uncertainty principle are not apparent with large systems because of the small size of h. However, the principle is of fundamental importance in the behaviour of systems on the atomic scale. For example, the principle explains the inherent width of spectral lines, if the lifetime of an atom in an excited state is very short there is a large uncertainty in its energy and line resulting from a transition is broad.
One consequence of the uncertainty principle is that predicting the behaviour of a system and the macroscopic principle of causality cannot apply at the atomic level is impossible fully. Quantum mechanics give a statistical description of the behaviour of physical systems.
Nevertheless, while there is uncertainty on the subatomic level, quantum physics successfully predicts the overall outcome of subatomic events, a fact that firmly relates it to the macroscopic world, that is, the one in which we live.
In 1934 Italian-born American physicist Enrico Fermi began a series of experiments in which he used neutrons (subatomic particles without an electric charge) to bombard atoms of various elements, including uranium. The neutrons combined with the nuclei of the uranium atoms to produce what he thought were elements heavier than uranium, known as transuranium elements. In 1939 other scientists demonstrated that in these experiments’ Fermi had not formed heavier elements, but instead had achieved the splitting, or fission, of the uranium atom's nucleus. These early experiments led to the development of fission as both energy sources.
These fission studies, coupled with the development of particle accelerators in the 1950's, initiated a long and remarkable journey into the nature of subatomic particles that continues today. Far from being indivisible, scientists now know that atoms are made up of twelve fundamental particles known as quarks and leptons, which combine in different ways to make all the kinds of matter currently known.
Advances in particle physics have been closely linked to progress in cosmology. From the 1920's onward, when the American astronomer Edwin Hubble showed that the universe is expanding, cosmologists have sought to rewind the clock and establish how the universe began. Today, most scientists believe that the universe started with a cosmic explosion some time between ten and twenty billion years ago. However, the exact sequence of events surrounding its birth, and its ultimate fate, are still matters of ongoing debate.
Apart from their assimilations affiliated within the paradigms of science, Descartes was to posit the existence of two categorically different domains of existence for immaterial ideas-the res extensa and the res cognitans or the ‘extended substance’ and the ‘thinking substance. Descartes defined the extended substance as the realm of physical reality within primary mathematical and geometrical forms resides and thinking substance as the realm of human subjective reality. Given that Descartes distrusted the information from the senses to the point of doubting the perceived results of repeatable scientific experiments, how did he conclude that our knowledge of the mathematical ideas residing only in mind or in human subjectivity was accurate, much less the absolute truth? He did so by making a lap of faith-God constructed the world, said Descartes, in accordance with the mathematical ideas that our minds are capable of uncovering in their pristine essence. The truth of classical physics as Descartes viewed them were quite literally ‘revealed’ truths, and it was this seventeenth-century metaphysical presupposition that became in the history of science what we term the ‘hidden ontology of classical epistemology.’
While classical epistemology would serve the progress of science very well, It also presented us with a terrible dilemma about the relationship between ‘mind’ and the ‘world’. If there is no real or necessary correspondence between non-mathematical ideas in subjective reality and external physical reality, how do we now that the world in which we live, breath, and have our Being, then perish in so that we undeniably exist? Descartes’s resolution of this dilemma took the form of an exercise. He asked us to direct our attention inward and to divest our consciousness of all awareness of eternal physical reality. If we do so, he concluded, the real existence of human subjective reality could be confirmed.
As it turned out, this resolution was considerably more problematic and oppressive than Descartes could have imaged. ‘I think, Therefore, I am’ may be a marginally persuasive way of confirming the real existence e of the thinking self. However, the understanding of physical reality that obliged Descartes and others to doubt the existence of this self implied that the separation between the subjective world, or the world of life, and the real world of physical reality was ‘absolute.’
Our purported new understanding of the relationship between mind and world is framed within the larger context, that of the history of mathematical physics, and the organs and extensions of the classical view of the foundations of scientific knowledge. The various ways that physicists have attempted to obviate previous challenges to the efficacy of classical epistemology, this was made so, as to serve as background for a new relationship between parts and wholes in quantum physics. As, well, as similar views drawn on or upon the relationship that had emerged in the so-called ‘new biology’ and in recent studies of the evolution of modern humans.
Nevertheless, at the end of such as this arduous journey lie two conclusions that should make possible that first, there is no basis in contemporary physics or biology for believing in the stark Cartesian division between mind and world, that some have alternatively given to describe as ‘the disease of the Western mind’. Secondly, there is a new basis for dialogue between two cultures that are now badly divided and very much un need of an enlarged sense of common understanding and shared purpose; let us briefly consider the legacy in Western intellectual life of the stark division between mind and world sanctioned by classical physics and formalized by Descartes.
The first scientific revolution of the seventeenth century freed Western civilization from the paralysing and demeaning forces of superstition, laid the foundations for rational understanding and control of the processes of nature, and ushered in an era of technological innovation and progress that provided untold benefits for humanity. Nevertheless, as classical physics progressively dissolved the distinction between heaven and earth and united the universe in a shared and communicable frame of knowledge, it presented us with a view of physical reality that was totally alien from the world of everyday life.
Philosophy, quickly realized that there was nothing in tis view of nature that could explain o provide a foundation for the mental, or for all that we know from direct experience cas distinctly human. In a mechanistic universe, he said, there is no privileged place or function for mind, and the separation between mind and matter is absolute. Descartes was also convinced, however, that the immaterial essences that gave form and structure to this universe were coded in geometrical and mathematical ideas, and this insight led to invent ‘algebraic geometry’.
A scientific understanding of these ideas could be derived, said Descartes, with the aid of precise deduction, and him also claimed that the contours of physical reality could be laid out in three-dimensional co-ordinates. Following the publication of Isaac Newton’s Principia Mathematica. In 1687, reductionism and mathematical modelling became the most powerful tools of modern science. The dream that the entire physical world would be known and mastered though the extension and refinement of mathematical theory became the central feature and guiding principle of scientific knowledge.
Descartes’s theory of knowledge starts with the quest for certainty, for an indubitable starting-point or foundation on the basis alone of which progress is possible. This is the method of investigating the extent of knowledge and its basis in reason or experience, it attempts to put knowledge upon a secure formation by first inviting us to suspend judgement on any proposition whose truth can be doubted, even as a bare possibility. The standards of acceptance are gradually raised as we are asked to doubt the deliverance of memory, the senses, and even reason, all of which are in principle capable of letting us down. The process is eventually dramatized in the figure of the evil-demon, or malin génie, whose aim is to deceive us, so that our sense, memories, and seasonings lead us astray. The task then becomes one of finding a demon-proof points of certainty, and Descartes produces this in the famous ‘Cogito ergo sum’, I think therefore I am’. It is on this slender basis that the correct use of our faculties has to be reestablished, but it seems as though Descartes has denied himself any materials to use in reconstructing the edifice of knowledge. He has a basis, but any way of building on it without invoking principles tat will not be demon-proof, and so will not meet the standards he had apparently set himself. It vis possible to interpret him as using ‘clear and distinct ideas’ to prove the existence of God, whose benevolence then justifies our use of clear and distinct ideas (‘God is no deceiver’): This is the notorious Cartesian circle. Descartes’s own attitude to this problem is not quite clear, at timers he seems more concerned with providing a stable body of knowledge, that our natural faculties will endorse, rather than one that meets the more severe standards with which he starts. For example, in the second set of Replies he shrugs off the possibility of ‘absolute falsity’ of our natural system of belief, in favour of our right to retain ‘any conviction so firm that it is quite incapable of being destroyed’. The need to add such natural belief to anything certified by reason Events eventually the cornerstone of Hume ‘s philosophy, and the basis of most 20th-century reactionism, to the method of doubt.
In his own time Rene Descartes’ conception of the entirely separate substance of the mind was recognized to give rise to insoluble problems of the nature of the causal efficacy to the action of God. Events in the world merely form occasions on which God acts so as to bring about the events normally accompanying them, and thought of as their effects, although the position is associated especially with Malebrallium, it is much older, many among the Islamic philosophies, their processes for adducing philosophical proofs to justify elements of religious doctrine. It plays the parallel role in Islam to that which scholastic philosophy played in the development of Christianity. The practitioners of kalam were known as the Mutakallimun. It also gives rise to the problem, insoluble in its own terms, of ‘other minds’. Descartes’s notorious denial that nonhuman animals are conscious is a stark illustration of th problem.
In his conception of matter Descartes also gives preference to rational cogitation over anything derived from the senses., since we can conceive of the nature of a ‘ball of wax’ surviving changes to its sensible qualities, matter is not an empirical concept, but eventually an entirely geometrical one, with extension and motion as its only physical nature. Descartes’s thought here is reflected in Leibniz’s view, as held later by Russell, that the qualities of sense experience have no resemblance to qualities of things, so that knowledge of the external world is essentially knowledge of structure rather than of filling. On this basis Descartes erects a remarkable physics. Since matter is in effect the same as extension there can be no empty space or ‘void’, since there is no empty space motion is not a question of occupying previously empty space, but is to be thought of in terms of vortices (like the motion of a liquid).
Although the structure of Descartes’s epistemology, theory of mind, and theory of matter have been rejected many times, their relentless exposure of the hardest issues, their exemplary clarity, and even their initial plausibility all contrive to make him the central point of reference for modern philosophy.
It seems, nonetheless, that the radical separation between mind and nature formalized by Descartes served over time to allow scientists to concentrate on developing mathematical descriptions of matter as pure mechanisms without any concerns about is spiritual dimension or ontological foundations. In the meantime, attempts to rationalize, reconcile, or eliminate Descartes’s stark division between mind and matter became perhaps te most cental feature of Western intellectual life.
Philosophers in the like of John Locke, Thomas Hobbes, and David Hume tried to articulate some basis for linking the mathematical describable motions of mater with linguistic representations of external reality in the subjective space of mind. Descartes’ compatriot Jean-Jacques Rousseau reified nature as the ground of human consciousness in a state of innocence and proclaimed that “Liberty, Equality, Fraternity” are the guiding principles of this consciousness. Rousseau also made godlike the ideas o the ‘general will’ of the people to achieve these goals and declare that those who do not conform to this will were social deviants.
Evenhandedly, Rousseau’s attempt to posit a ground for human consciousness by reifying nature was revived in a measure more different in form by the nineteenth-century Romantics in Germany, England, and the United Sates. Goethe and Friedrich Schelling proposed a natural philosophy premised on ontological monism (the idea that God, man, and nature are grounded in an indivisible spiritual Oneness) and argued for the reconciliation of mind and matter with an appeal to sentiment, mystical awareness, and quasi-scientific musing. In Goethe’s attempt to wed mind and matter, nature became a mindful agency that ‘loves illusion’. Shrouds man in mist, ‘ presses him to her heart’, and punishes those who fail to see the ‘light’. Schelling, in his version of cosmic unity, argued that scientific facts were at best partial truths and that the mindful creative spirit that unifies mind and matter is progressively moving toward self-realization and undivided wholeness.
Descartes believed there are two basic kinds of things in the world, a belief known as substance dualism. For Descartes, the principles of existence for these two groups of things -bodies and minds-are completely different from one another: Bodies exist by being extended in space, while minds exist by being conscious. According to Descartes, nothing can be done to give a body thought and consciousness. No matter how we shape a body or combine it with other bodies, we cannot turn the body into a mind, a thing that is conscious, because being conscious is not a way of being extended.
For Descartes, a person consists of a human body and a human mind causally interacting with one another. For example, the intentions of a human being might have awaken that person’s limbs to move. In this way, the mind can affect the body. In addition, the sense organs of a human being may be affected by light, pressure, or sound, external sources that in turn affect the brain, affecting mental states. Thus, the body may affect the mind. Exactly how mind can affect body, and vice versa, is a central issue in the philosophy of mind, and is known as the mind-body problem. According to Descartes, this interaction of mind and body is peculiarly intimate. Unlike the interaction between a pilot and his ship, the connection between mind and body more closely resembles two substances that have been thoroughly mixed.
Because of the diversity of positions associated with existentialism, the term is impossible to define precisely. Certain themes common to virtually all existentialist writers can, however, be identified. The term itself suggests one major theme: the stress on concrete individual existence and, consequently, on subjectivity, individual freedom, and choice.
Most philosophers since Plato have held that the highest ethical good is the same for everyone; insofar as one approaches moral perfection, one resembles other morally perfect individuals. The 19th-century Danish philosopher Søren Kierkegaard, who was the first writer to call himself existential, reacted against this tradition by insisting that the highest good for the individual is to find his or her own unique vocation. As he wrote in his journal, “I must find a truth that is true for me . . . the idea for which I can live or die.” Other existentialist writers have echoed Kierkegaard's belief that one must choose one's own way without the aid of universal, objective standards. Against the traditional view that moral choice involves an objective judgment of right and wrong, existentialists have argued that no objective, rational basis can be found for moral decisions. The 19th-century German philosopher Friedrich Nietzsche further contended that the individual must decide which situations are to count as moral situations.
All existentialists have followed Kierkegaard in stressing the importance of passionate individual action in deciding questions of both morality and truth. They have insisted, accordingly, that personal experience and acting on one's own convictions are essential in arriving at the truth. Thus, the understanding of a situation by someone involved in that situation is superior to that of a detached, objective observer. This emphasis on the perspective of the individual agent has also made existentialists suspicious of systematic reasoning. Kierkegaard, Nietzsche, and other existentialist writers have been deliberately unsystematic in the exposition of their philosophies, preferring to express themselves in aphorisms, dialogues, parables, and other literary forms. Despite their antirationalist position, however, most existentialists cannot be said to be irrationalists in the sense of denying all validity to rational thought. They have held that rational clarity is desirable wherever possible, but that the most important questions in life are not accessible to reason or science. Furthermore, they have argued that even science is not as rational as is commonly supposed. Nietzsche, for instance, asserted that the scientific assumption of an orderly universe is for the most part a useful fiction.
Perhaps the most prominent theme in existentialist writing is that of choice. Humanity's primary distinction, in the view of most existentialists, is the freedom to choose. Existentialists have held that human beings do not have a fixed nature, or essence, as other animals and plants do; each human being makes choices that create his or her own nature. In the formulation of the 20th-century French philosopher Jean-Paul Sartre, existence precedes essence. Choice is therefore central to human existence, and it is inescapable; even the refusal to choose is a choice. Freedom of choice entails commitment and responsibility. Because individuals are free to choose their own path, existentialists have argued, they must accept the risk and responsibility of following their commitment wherever it leads.
Kierkegaard held that recognizing that one experiences is spiritually crucial not only a fear of specific objects but also a feeling of general apprehension, which he called dread. He interpreted it as God's way of calling each individual to make a commitment to a personally valid way of life. The word anxiety (German Angst) has a similarly crucial role in the work of the 20th-century German philosopher Martin Heidegger; anxiety leads to the individual's confrontation with nothingness and with the impossibility of finding ultimate justification for the choices he or she must make. In the philosophy of Sartre, the word nausea is used for the individual's recognition of the pure contingency of the universe, and the word anguish is used for the recognition of the total freedom of choice that confronts the individual at every moment.
Existentialism as a distinct philosophical and literary movement belongs to the 19th and 20th centuries, but elements of existentialism can be found in the thought (and life) of Socrates, in the Bible, and in the work of many premodern philosophers and writers.
The first to anticipate the major concerns of modern existentialism was the 17th-century French philosopher Blaise Pascal. Pascal rejected the rigorous rationalism of his contemporary René Descartes, asserting, in his Pensées (1670), that a systematic philosophy that presumes to explain God and humanity is a form of pride. Like later existentialist writers, he saw human life in terms of paradoxes: The human self, which combines mind and body, is itself a paradox and contradiction.
Kierkegaard, generally regarded as the founder of modern existentialism, reacted against the systematic absolute idealism of the 19th-century German philosopher Georg Wilhelm Friedrich Hegel, who claimed to have worked out a total rational understanding of humanity and history. Kierkegaard, on the contrary, stressed the ambiguity and absurdity of the human situation. The individual's response to this situation must be to live a totally committed life, and this commitment can only be understood by the individual who has made it. The individual therefore must always be prepared to defy the norms of society for the sake of the higher authority of a personally valid way of life. Kierkegaard ultimately advocated a ‘leap of faith’ into a Christian way of life, which, although incomprehensible and full of risk, was the only commitment he believed could save the individual from despair.
Nietzsche, who was not acquainted with the work of Kierkegaard, influenced subsequent existentialist thought through his criticism of traditional metaphysical and moral assumptions and through his espousal of tragic pessimism and the life-affirming individual will that opposes itself to the moral conformity of the majority. In contrast to Kierkegaard, whose attack on conventional morality led him to advocate a radically individualistic Christianity, Nietzsche proclaimed the “Death of God” and went on to reject the entire Judeo-Christian moral tradition in favour of a heroic pagan ideal.
Heidegger, like Pascal and Kierkegaard, reacted against an attempt to put philosophy on a conclusive rationalistic basis-in this case the phenomenology of the 20th-century German philosopher Edmund Husserl. Heidegger argued that humanity finds itself in an incomprehensible, indifferent world. Human beings can never hope to understand why they are here; instead, each individual must choose a goal and follow it with passionate conviction, aware of the certainty of death and the ultimate meaninglessness of one's life. Heidegger contributed to existentialist thought an original emphasis on being and ontology as well as on language.
Sartre first gave the term existentialism general currency by using it for his own philosophy and by becoming the leading figure of a distinct movement in France that became internationally influential after World War II. Sartre's philosophy is explicitly atheistic and pessimistic; he declared that human beings require a rational basis for their lives but are unable to achieve one, and thus human life is a ‘futile passion’. Sartre nevertheless insisted that his existentialism be a form of humanism, and he strongly emphasized human freedom, choice, and responsibility. He eventually tried to reconcile these existentialist concepts with a Marxist analysis of society and history.
Although existentialist thought encompasses the uncompromising atheism of Nietzsche and Sartre and the agnosticism of Heidegger, its origin in the intensely religious philosophies of Pascal and Kierkegaard foreshadowed its profound influence on 20th-century theology. The 20th-century German philosopher Karl Jaspers, although he rejected explicit religious doctrines, influenced contemporary theology through his preoccupation with transcendence and the limits of human experience. The German Protestant theologians Paul Tillich and Rudolf Bultmann, the French Roman Catholic theologian Gabriel Marcel, the Russian Orthodox philosopher Nikolay Berdyayev, and the German Jewish philosopher Martin Buyer inherited many of Kierkegaard's concerns, especially that a personal sense of authenticity and commitment is essential to religious faith.
A number of existentialist philosophers used literary forms to convey their thought, and existentialism has been as vital and as extensive a movement in literature as in philosophy. The 19th-century Russian novelist Fyodor Dostoyevsky is probably the greatest existentialist literary figure. In Notes from the Underground (1864), the alienated antihero rages against the optimistic assumptions of rationalist humanism. The view of human nature that emerges in this and other novels of Dostoyevsky is that it is unpredictable and perversely self-destructive; only Christian love can save humanity from itself, but such love cannot be understood philosophically. As the character Alyosha says in The Brothers Karamazov (1879-80), “We must love life more than the meaning of it.”
In the 20th century, the novels of the Austrian Jewish writer Franz Kafka, such as The Trial (1925; trans. 1937) and The Castle (1926; trans. 1930), present isolated men confronting vast, elusive, menacing bureaucracies; Kafka's themes of anxiety, guilt, and solitude reflect the influence of Kierkegaard, Dostoyevsky, and Nietzsche. The influence of Nietzsche is also discernible in the novels of the French writers André Malraux and in the plays of Sartre. The work of the French writer Albert Camus is usually associated with existentialism because of the prominence in it of such themes as the apparent absurdity and futility of life, the indifference of the universe, and the necessity of engagement in a just cause. Existentialist themes are also reflected in the th eater of the absurd, notably in the plays of Samuel Beckett and Eugène Ionesco. In the United States, the influence of existentialism on literature has been more indirect and diffuse, but traces of Kierkegaard's thought can be found in the novels of Walker Percy and John Updike, and various existentialist themes are apparent in the work of such diverse writers as Norman Mailer, John Barth, and Arthur Miller.
The fatal flaw of pure reason is, of course, the absence of emotion, and purely rational explanations of the division between subjective reality and external reality had limited appeal outside the community of intellectuals. The figure most responsible for infusing our understanding of Cartesian dualism with emotional content was the death of God theologian Friedrich Nietzsche. After declaring that God and ‘divine will’ do not exist, Nietzsche reified the ‘essences’ of consciousness in the domain of subjectivity as the ground for individual ‘will’ and summarily dismissed all pervious philosophical attempts to articulate the ‘will to truth’. The problem, claimed Nietzsche, is that earlier versions of the ‘will to power’ disguise the fact that all allege truths were arbitrarily created in the subjective reality of the individual and are expression or manifestations of individual ‘will’.
In Nietzsche’s view, the separation between mind and mater is more absolute and total than had previously been imagined. Based on the assumption that there is no real or necessary correspondences between linguistic constructions of reality in human subjectivity and external reality, he declared that we are all locked in ‘a prison house of language’. The prison as he conceived it, however, it was also a ‘space’ where the philosopher can examine the ‘innermost desires of his nature’ and articulate a new massage of individual existence founded on will.
Those who fail to enact their existence in this space, says Nietzsche, are enticed into sacrificing their individuality on the nonexistent altars of religious beliefs and democratic or socialist ideals and become, therefore, members of the anonymous and docile crowd. Nietzsche also invalidated the knowledge claims of science in the examination of human subjectivity. Science, he said, not only exalted natural phenomena and favours reductionistic examinations of phenomena at the expense of mind. It also seeks to educe mind to a mere material substance, and thereby to displace or subsume the separateness and uniqueness of mind with mechanistic description that disallow any basis for te free exerciser of individual will.
Nietzsche’s emotionally charged defence of intellectual freedom and his radical empowerment of mind as the maker and transformer of the collective fictions that shape human reality in a soulful mechanistic inverse proved terribly influential on twentieth-century thought. Nietzsche sought to reinforce his view of the subjective character of scientific knowledge by appealing to an epistemological crisis over the foundations of logic and arithmetic that arose during the last three decades of the nineteenth century. Though a curious course of events, attempts by Edmund Husserl, a philosopher trained in higher math and physics, to resolve this crisis resulted in a view of the character of human consciousness that closely resembled that of Nietzsche.
Friedrich Nietzsche is openly pessimistic about the possibility of knowledge. ‘We simply lack any organ for knowledge, for ‘truth’: we know (or believe or imagine) just as much as may be useful in the interests of the human herd, the species: and even what is called ‘utility’ is ultimately also a mere belief, something imaginary and perhaps precisely that most calamitous stupidity of which we will not perish some day’ (The Gay Science).
This position is very radical, Nietzsche does not simply deny that knowledge, construed as the adequate representation of the world by the intellect, exists. He also refuses the pragmatist identification of knowledge and truth with usefulness: he writes that we think we know what we think is useful, and that we can be quite wrong about the latter.
Nietzsche’s view, his ‘Perspectivism’, depends on his claim that there is no sensible conception of a world independent of human interpretation and to which interpretations would correspond if hey were to constitute knowledge. He sum up this highly controversial position in The Will to Power: ‘Facts are precisely what there is not. Only interpretation’.
It is often claimed that Perspectivism is self-undermining. If the thesis that all views are interpretations is true then, it is argued there is at least one view that is not an interpretation. If, on the other hand, the thesis is itself an interpretation, then there is no reason to believe that it is true, and it follows again that nit every view is an interpretation.
Yet this refutation assume that if a view, like Perspectivism itself, is an interpretation it is wrong. This is not the case. To call any view, including Perspectivism, an interpretation is to say that it can be wrong, which is true of all views, and that is not a sufficient refutation. To show the Perspectivism is literally false producing another view superior to it on specific epistemological grounds is necessary.
Perspectivism does not deny that particular views can be true. Like some versions of cotemporary anti-realism, it attributes to specific approaches truth in relation t o facts specified internally those approaches themselves. Bu t it refuses to envisage a single independent set of facts, To be accounted for by all theories. Thus Nietzsche grants the truth of specific scientific theories does, however, deny that a scientific interpretation can possibly be ‘the only justifiable interpretation of the world’ (The Gay Science): Neither t h fact science addresses nor the methods it employs are privileged. Scientific theories serve the purposes for which hey have been devised, but these have no priority over the many other purposes of human life. The existence of many purposes and needs relative to which the value of theories is established-another crucial element of Perspectivism is sometimes thought to imply a reason relative, according to which no standards for evaluating purposes and theories can be devised. This is correct only in that Nietzsche denies the existence of single set of standards for determining epistemic value, but holds that specific views can be compared with and evaluated in relation to one another the ability to use criteria acceptable in particular circumstances does not presuppose the existence of criteria applicable in all. Agreement is therefore not always possible, since individuals may sometimes differ over the most fundamental issues dividing them.
Still, Nietzsche would not be troubled by this fact, which his opponents too also have to confront only he would argue, to suppress it by insisting on the hope that all disagreements are in particular eliminable even if our practice falls woefully short of the ideal. Nietzsche abandons that ideal. He considers irresoluble disagreement and essential part of human life.
Knowledge for Nietzsche is again material, but now based on desire and bodily needs more than social refinements Perspectives are to be judged not from their relation to the absolute but on the basis of their effects in a specific era. The possibility of any truth beyond such a local, pragmatic one becomes a problem in Nietzsche, since either a noumenal realm or an historical synthesis exists to provide an absolute criterion of adjudication for competing truth claims: what get called truths are simply beliefs that have been for so long that we have forgotten their genealogy? In this Nietzsche reverses the Enlightenment dictum that truth is the way to liberation by suggesting that trying classes in as far as they are considered absolute for debate and conceptual progress and cause as opposed to any ambient behaviour toward the ease of which backwardness and unnecessary misery. Nietzsche moves back and forth without revolution between the positing of trans-histories; truth claims, such as his claim about the will to power, and a kind of epistemic nihilism that calls into question not only the possibility of truth but the need and desire of it as well. However, perhaps what is most important, Nietzsche introduces the notion that truth is a kind of human practice, in a game whose rules are contingent rather than necessary it. The evaluation of truth claims should be based of their strategic efforts, not their ability to represent a reality conceived of as separate as of an autonomous of human influence, for Nietzsche the view that all truth is truth from or within a particular perspective. The perspective may be a general human pin of view, set by such things as the nature of our sensory apparatus, or it may be thought to be bound by culture, history, language, class or gender. Since there may be many perspectives, there are also different families of truth. The term is frequently applied to, of course Nietzsche’s philosophy.
The best-known disciples of Husserl was Martin Heidegger, and the work of both figures greatly influenced that of the French atheistic existentialist Jean-Paul Sartre. The work of Husserl, Heidegger and Sartre became foundational to that of the principle architects of philosophical postmodernism, the deconstructionists Jacques Lacan, Roland Bathes, Michel Foucault and Jacques Derrida, this direct linkage among the nineteenth-century crises about epistemological foundations of physics and the origins of philosophical postmodernism served to perpetuate the Cartesian two-world dilemma in an even more oppressive form
Of Sartre’s main philosophical work, Being and Nothingness, Sartre examines the relationships between Being For-itself (consciousness) and Being In-itself (the non-conscious world). He rejects central tenets of the rationalalist and empiricist traditions, calling the view that the mind or self is a thing or substance. ‘Descartes’s substantialist illusion’, and claiming also that consciousness dos not contain ideas or representations . . . are idolist invented by the psychologists. Sartre also attacks idealism in the forms associated with Berkeley and Kant, and concludes that his account of the relationship between consciousness and the world is neither realist nor idealist.
Sartre also discusses Being For-others, which comprises the aspects of experience about interactions with other minds.. His views are subtle: roughly, he holds that one’s awareness of others is constituted by feelings of shame, pride, and so on.
Sartre’s rejection of ideas, and the denial of idealism, appear to commit him to direct realism in the theory of perception. This is neither inconsistent with his claim as been non-realist nor idealist, since by ‘realist’ he means views that allow for the mutual independence or in-principle separability of mind and world. Against this Sartre emphasizes, after Heidegger, that perceptual experience has an active dimension, in hat it is a way of interacting and dealing with the world, than a way of merely contemplating it (‘activity, as spontaneous, unreflecting consciousness, constitutes a certain existential stratum in the world’). Consequently, he holds that experience is richer, and open to more aspects of the world, than empiricist writers customarily claim:
When I run after a streetcar . . . there is consciousness of-the-streetcar-having-to-be-overtaken, etc., . . . I am then plunged into the world of objects, it is they that constitute the unity of my consciousness, it is they that present themselves with values, with attractive nd repellent qualities . . .
Relatedly, he insists that I experience material things as having certain potentialities -for-me (’nothingness’). I see doors and bottles as openable, bicycles as ridable (these matters are linked ultimately to the doctrine of extreme existentialist freedom). Similarly, if my friend is not where I expect to meet her, then I experience her absence ‘as a real event’.
These Phenomenological claims are striking and compelling, but Sartre pay insufficient attention to such things as illusions and hallucinations, which are normally cited as problems for direct realists. In his discussion of mental imagery, however, he describes the act of imaging as a ‘transformation’ of ‘psychic material’. This connects with his view that even a physical image such as a photograph of a tree does not figure as an object of consciousness when it is experienced as a tree-representation (than as a piece of coloured cards). Nonetheless, the fact remains that the photograph continues to contribute to the character of the experience. Given this, seeing how Sartre avoids positing a mental analogue of a photograph for episodes of mental imaging is hard, and harder still to reconcile this with his rejection of visual representations. If ones image is regarded as debased and the awareness of awakening is formally received as a differential coefficient of perceptual knowledge, but this merely rises once more the issue of perceptual illusion and hallucination, and the problem of reconciling them are dialectally the formalization built upon realism.
Much of Western religion and philosophical thought since the seventeenth century has sought to obviate this prospect with an appeal to ontology or to some conception of God or Being. Yet we continue to struggle, as philosophical postmodernism attests, with the terrible prospect by Nietzsche-we are locked in a prison house of our individual subjective realities in a universe that is as alien to our thought as it is to our desires. This universe may seem comprehensible and knowable in scientific terms, and science does seek in some sense, as Koyré puts it, to ‘find a place for everything.’ Nonetheless, the ghost of Descartes lingers in the widespread conviction that science does not provide a ‘place for man’ or for all that we know as distinctly human in subjective reality.
Nonetheless, after The Gay Science (1882) began the crucial exploration of self-mastery. The relations between reason and power, and the revelation of the unconscious striving after power that provide the actual energy for the apparent self-denial of the ascetic and the martyred was during this period that Nietzsche’s failed relationship with Lou Salome resulted in the emotional crisis from which Also sprach Zarathustra (1883-5, trans., as Thus Spoke Zarathustra) signals a recovery. This work is frequently regarded as Nietzsche’s masterpiece. It was followed by Jenseits von Gut and Böse (1887), trans., as Beyond Good and Evil); Zur Genealogie der Moral (1887, trans., as, The Genealogy of Moral.)
In Thus Spake Zarathustra (1883-85), Friedrich Nietzsche introduced in eloquent poetic prose the concepts of the death of God, the superman, and the will to power. Vigorously attacking Christianity and democracy as moralities for the ‘weak herd’, he argued for the ‘natural aristocracy’ of the superman who, driven by the ‘will to power’, celebrates life on earth rather than sanctifying it for some heavenly reward. Such a heroic man of merit has the courage to ‘live dangerously’ and thus rise above the masses, developing his natural capacity for the creative use of passion.
Also known as radical theology, this movement flourished in the mid 1960s. As a theological movement it never attracted a large following, did not find a unified expression, and passed off the scene as quickly and dramatically as it had arisen. There is even disagreement as to whom its major representatives were. Some identify two, and others three or four. Although small, the movement attracted attention because it was a spectacular symptom of the bankruptcy of modern theology and because it was a journalistic phenomenon. The very statement "God is dead" was tailor-made for journalistic exploitation. The representatives of the movement effectively used periodical articles, paperback books, and the electronic media. This movement gave expression to an idea that had been incipient in Western philosophy and theology for some time, the suggestion that the reality of a transcendent God at best could not be known and at worst did not exist at all. Philosopher Kant and theologian Ritschl denied that one could have a theoretical knowledge of the being of God. Hume and the empiricist for all practical purposes restricted knowledge and reality to the material world as perceived by the five senses. Since God was not empirically verifiable, the biblical world view was said to be mythological and unacceptable to the modern mind. Such atheistic existentialist philosophers as Nietzsche despaired even of the search of God; it was he who coined the phrase "God is dead" almost a century before the death of God theologians.
Mid-twentieth century theologians not associated with the movement also contributed to the climate of opinion out of which death of God theology emerged. Rudolf Bultmann regarded all elements of the supernaturalistic, theistic world view as mythological and proposed that Scripture be demythologized so that it could speak its message to the modern person.
Paul Tillich, an avowed anti supernaturalist, said that the only nonsymbiotic statement that could be made about God was that he was being itself. He is beyond essence and existence; therefore, to argue that God exists is to deny him. It is more appropriate to say God does not exist. At best Tillich was a pantheist, but his thought borders on atheism. Dietrich Bonhoeffer (whether rightly understood or not) also contributed to the climate of opinion with some fragmentary but tantalizing statements preserved in Letters and Papers from Prison. He wrote of the world and man ‘coming of age’, of ‘religionless Christianity’, of the ‘world without God’, and of getting rid of the ‘God of the gaps’ and getting along just as well as before. It is not always certain what Bonhoeffer meant, but if nothing else, he provided a vocabulary that later radical theologians could exploit.
It is clear, then, that as startling as the idea of the death of God was when proclaimed in the mid 1960s, it did not represent as radical a departure from recent philosophical and theological ideas and vocabulary as might superficially appear.
Just what was death of God theology? The answers are as varied as those who proclaimed God's demise. Since Nietzsche, theologians had occasionally used "God is dead" to express the fact that for an increasing number of people in the modern age God seems to be unreal. Nonetheless, the idea of God's death began to have special prominence in 1957 when Gabriel Vahanian published a book entitled God is Dead. Vahanian did not offer a systematic expression of death of God theology. Instead, he analysed those historical elements that contributed to the masses of people accepting atheism not so much as a theory but as a way of life. Vahanian himself did not believe that God was dead. Still, he urged that there be a form of Christianity that would recognize the contemporary loss of God and exert its influence through what was left. Other proponents of the death of God had the same assessment of God's status in contemporary culture, but were to draw different conclusions.
Thomas J. J. Altizer believed that God had really died. Nonetheless, Altizer often spoke in exaggerated and dialectic language, occasionally with heavy overtones of Oriental mysticism. Sometimes knowing exactly what Altizer meant when he spoke in dialectical opposites is difficult such as "God is dead, thank God" Apparently the real meaning of Altizer's belief that God had died is to be found in his belief in God's immanence. To say that God has died is to say that he has ceased to exist as a transcendent, supernatural being. Alternately, he has become fully immanent in the world. The result is an essential identity between the human and the divine. God died in Christ in this sense, and the process has continued time and again since then. Altizer claims the church tried to give God life again and put him back in heaven by its doctrines of resurrection and ascension. However, the traditional doctrines about God and Christ must be repudiated because man has discovered after nineteen centuries that God does not exist. Christians must even now will the death of God by which the transcendent becomes immanent.
For William Hamilton the death of God describes the event many have experienced over the last two hundred years. They no longer accept the reality of God or the meaningfulness of language about him. non theistic explanations have been substituted for theistic ones. This trend is irreversible, and everyone must come to terms with the historical-cultural -death of God. God's death must be affirmed and the secular world embraced as normative intellectually and good ethically. Doubtlessly, Hamilton was optimistic about the world, because he was optimistic about what humanity could do and was doing to solve its problems.
Paul van Buren is usually associated with death of God theology, although he himself disavowed this connection. Yet, his disavowal seems hollow in the light of his book The Secular Meaning of the Gospel and his article "Christian Education Post Mortem Dei." In the former he accepts empiricism and the position of Bultmann that the world view of the Bible is mythological and untenable to modern people. In the latter he proposes an approach to Christian education that does not assume the existence of God but does assume ‘the death of God’ and that ‘God is gone’.
Van Buren was concerned with the linguistic aspects of God's existence and death. He accepted the premise of empirical analytic philosophy that real knowledge and meaning can be conveyed only by language that is empirically verifiable. This is the fundamental principle of modern secularists and is the only viable option in this age. If only empirically verifiable language is meaningful, ipso facto all language that refers to or assumes the reality of God is meaningless, since one cannot verify God's existence by any of the five senses. Theism, belief in God, is not only intellectually untenable, it is meaningless. In The Secular Meaning of the Gospel van Buren seeks to reinterpret the Christian faith without reference to God. One searches the book in vain for even one clue that van Buren is anything but a secularist trying to translate Christian ethical values into that language game. There is a decided shift in van Buren's later book Discerning the Way, however.
In retrospect, there was clearly no single death of God theology, only death of God theologies. Their real significance was that modern theologies, by giving up the essential elements of Christian belief in God, had logically led to what were really antitheologies. When the death of God theologies passed off the scene, the commitment to secularism remained and manifested itself in other forms of secular theology in the late 1960s and the 1970s.
Nietzsche is unchallenged as the most insightful and powerful critic of the moral climate of the 19th century (and of what of it remains in ours). His exploration of unconscious motivation anticipated Freud. He is notorious for stressing the ‘will to power’ that is the basis of human nature, the ‘resentment’ that comes when it is denied its basis in action, and the corruptions of human nature encouraged by religion, such as Christianity, that feed on such resentment. Yet the powerful human beings who escapes all this, the Ubermensch, is not the ‘blood beast’ of later fascism: It is a human being who has mastered passion, risen above the senseless flux, and given creative style to his or her character. Nietzsche’s free spirits recognize themselves by their joyful attitude to eternal return. He frequently presents the creative artist rather than the warlord as his best exemplar of the type, but the disquieting fact remains that he seems to leave himself no words to condemn any uncaged beasts of pre y who best find their style by exerting repulsive power find their style by exerting repulsive power over others. This problem is no t helped by Nietzsche’s frequently expressed misogyny, although in such matters the interpretation of his many-layered and ironic writings is no always straightforward. Similarly y, such
Anti-Semitism as has been found in his work is balanced by an equally vehement denunciation of anti-Semitism, and an equal or greater dislike of the German character of his time.
Nietzsche’s current influence derives not only from his celebration of will, but more deeply from his scepticism about the notions of truth and act. In particular, he anticipated any of the central tenets of postmodernism: an aesthetic attitude toward the world that sees it as a ‘text’; the denial of facts; the denial of essences; the celebration of the plurality of interpretation and of the fragmented self, as well as the downgrading of reason and the politicization of discourse. All awaited rediscovery in the late 20th century. Nietzsche also has the incomparable advantage over his followers of being a wonderful stylist, and his Perspectivism is echoed in the shifting array of literary devices-humour, irony, exaggeration, aphorisms, verse, dialogue, parody-with that he explores human life and history.
Yet, it is nonetheless, that we have seen, the origins of the present division that can be traced to the emergence of classical physics and the stark Cartesian division between mind and bodily world are two separate substances, the self is as it happened associated with a particular body, but is self-subsisting, and capable of independent existence, yet Cartesian duality, much as the ‘ego’ that we are tempted to imagine as a simple unique thing that makes up our essential identity, but, seemingly sanctioned by this physics. The tragedy of the Western mind, well represented in the work of a host of writers, artists, and intellectual, is that the Cartesian division was perceived as uncontrovertibly real.
Beginning with Nietzsche, those who wished to free the realm of the mental from the oppressive implications of the mechanistic world-view sought to undermine the alleged privileged character of the knowledge called physicians with an attack on its epistemological authority. After Husserl tried and failed to save the classical view of correspondence by grounding the logic of mathematical systems in human consciousness, this not only resulted in a view of human consciousness that became characteristically postmodern. It also represents a direct link with the epistemological crisis about the foundations of logic and number in the late nineteenth century that foreshadowed the epistemological crisis occasioned by quantum physics beginning in the 1920's. This, as a result in disparate views on the existence of oncology and the character of scientific knowledge that fuelled the conflict between the two.
If there were world enough and time enough, the conflict between each that both could be viewed as an interesting artifact in the richly diverse coordinative systems of higher education. Nevertheless, as the ecological crisis teaches us, the ‘old enough’ capable of sustaining the growing number of our life firms and the ‘time enough’ that remains to reduce and reverse the damage we are inflicting on this world ae rapidly diminishing. Therefore, put an end to the absurd ‘betweeness’ and go on with the business of coordinate human knowledge in the interest of human survival in a new age of enlightenment that could be far more humane and much more enlightened than any has gone before.
It now, which it is, nonetheless, that there are significant advances in our understanding to a purposive mind. Cognitive science is an interdisciplinary approach to cognition that draws primarily on ideas from cognitive psychology, artificial intelligence, linguistics and logic. Some philosophers may be cognitive scientists, and others concern themselves with the philosophy of cognitive psychology and cognitive science. Since inauguration of cognitive science these disciplines have attracted much attention from certain philosophers of mind. This has changed the character of philosophy of mind, and there are areas where philosophical work on the nature of mind is continuous with scientific work. Yet, the problems that make up this field concern the ways of ‘thinking’ and ‘mental properties’ are those that these problems are standardly and traditionally regarded within philosophy of mind than those that emerge from the recent developments in cognitive science. The cognitive aspect is what has to be understood is to know what would make the sentence true or false. It is frequently identified with the truth cognition of the sentence. Justly as the scientific study of precesses of awareness, thought, and mental organization, often by means of a computer modelling or artificial intelligence research. Contradicted by the evidence, it only has to do with is structure and the way it functioned, that is just because a theory does not mean that the scientific community currently accredits it. Generally, there are many theories, though technically scientific, have been rejected because the scientific evidence is strangely against it. The historical enquiry into the evolution of self-consciousness, developing from elementary sense experience to fully rational, free, thought processes capable of yielding knowledge the presented term, is associated with the work and school of Husserl. Following Brentano, Husserl realized that intentionality was the distinctive mark of consciousness, and saw in it a concept capable of overcoming traditional mind-body dualism. The stud y of consciousness, therefore, maintains two sides: a conscious experience can be regarded as an element in a stream of consciousness, but also as a representative of one aspect or ‘profile’ of an object. In spite of Husserl’s rejection of dualism, his belief that there is a subject-matter remaining after epoch or bracketing of the content of experience, associates him with the priority accorded to elementary experiences in the parallel doctrine of phenomenalism, and phenomenology has partly suffered from the eclipse of that approach to problems of experience and reality. However, later phenomenologists such as Merleau-Ponty do full justice to the world-involving nature of Phenomenological theories are empirical generalizations of data experience, or manifest in experience. More generally, the phenomenal aspects of things are the aspects that show themselves, than the theoretical aspects that are inferred or posited in order to account for them. They merely described the recurring process of nature and do not refer to their cause or that, in the words of J.S. Mill, ‘objects are the permanent possibilities of sensation’. To inhabit a world of independent, external objects is, on this view, to be the subject of actual and possible orderly experiences. Espoused by Russell, the view issued in a programme of translating talk about physical objects and their locations into talking about possible experience. The attempt is widely supposed to have failed, and the priority the approach gives to experience has been much criticized. It is more common in contemporary philosophy to see experience as itself a construct from the actual way of the world, than the other way round.
Phenomenological theories are also called ‘scientific laws’ ‘physical laws’ and ‘natural laws.’ Newton’s third law is one example. It says that every action ha an equal and opposite reaction. ‘Explanatory theories’ attempt to explain the observations rather than generalized them. Whereas laws are descriptions of empirical regularities, explanatory theories are conceptual constrictions to explain why the data exit, for example, atomic theory explains why we see certain observations, the same could be said with DNA and relativity, Explanatory theories are particularly helpful in such cases where the entities (like atoms,
DNA . . . ) cannot be directly observed.
What is knowledge? How does knowledge get to have the content it has? The problem of defining knowledge in terms of true belief plus some favoured relation between the believer and the facts begun with Plato, in that knowledge is true belief plus logos, as it is what enables us to apprehend the principle and firms, i.e., an aspect of our own reasoning.
What makes a belief justified for what measures of belief is knowledge? According to most epistemologists, knowledge entails belief, so that to know that such and such is the case. None less, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These arguments are given by philosophers who think that knowledge and belief or facsimile, are mutually incompatible (the incompatibility thesis) or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, but the two may also coexist (the separability thesis). The incompatibility thesis that hinged on the equation of knowledge with certainty. The assumption that we believe in the truth of claim we are not certain about its truth. Given that belief always involves uncertainty, while knowledge never does, believing something rules out the possibility of knowledge knowing it. Again, given to no reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, to suggest otherwise, that we cease to believe things about which we are completely confident is bizarre.
A. D. Woozley (1953) defends a version of the separability thesis. Woozley’s version that deal with psychological certainty than belief per se, is that knowledge can exist without confidence about the item known, although knowledge might also be accompanied by confidence as well. Woozley says, ‘what I can Do, where what I can do may include answering questions.’ on the basis of this remark he suggests that even when people are unsure of the truth of a claim, they might know that the claim is true. We unhesitatingly attribute knowledge to people that correct responses on examinations if those people show no confidence in their answers. Woozley acknowledges however, that it would be odd for those who lack confidence to claim knowledge. Saying it would be peculiar, ‘I know it is correct.’ but this tension; still ‘I know is correct.’ Woozley explains, using a distinction between condition under which are justified in making a claim (such as a claim to know something) and conditioned under which the claim we make is true. While ‘I know such and such’ might be true even if I answered whether such and such holds, nonetheless claiming that ‘I know that such should be inappropriate for me and such unless I was sure of the truth of my claim.’
Colin Redford (1966) extends Woozley’s defence of the separability thesis. In Redford’s view, not only in knowledge compatible with the lacking of certainty, it is also compatible with a complete lack of belief. He argues by example, in this one example, Jean had forgotten that he learned some English history years prior and yet he is able to give several correct responses to questions such as, ‘When did the Battle of Hastings occur?’ since he forgot that the battle of Hastings took place in 1066 in history, he considers his correct response to be no more than guesses. Thus when he says that the Battle of Hastings took place in 1066 he would deny having the belief that the Battle of Hasting took place in 1066.
Those who agree with Radford’s defence of the separation thesis will probably think of belief as an inner state that can be directed through introspection. That Jean lacks’ beliefs out English history are plausible on this Cartesian picture since Jean does not find himself with the belief out of which the English history when with any beliefs about English history when he seeks them out. One might criticize Radford, however, by rejecting the Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious. For example, (1859), according to which having beliefs is a matter of the way people are disposed to behave (and has not Radford already adopted a behaviourist conception of knowledge?). since Jean gives the correct response when queried, a form of verbal behaviour, a behaviourist would be tempted to credit him with the belief that the battle of Hastings occurred in 1066.
Once, again, but the jargon is attributable to different attitudinal values. AS, D. M. Armstrong (1973) makes a different task against Radford. Jean does know that the Battle of Hastings took place in 1066. Armstrong will grant Radford that points, which in fact, Armstrong suggests that Jean believe that 1066 is not the date the Battle of Hastings occur. For Armstrong equates the belief of such and such is just possible bu t no more than just possible with the belief that such and such is not the case. However, Armstrong insists Jean also believe that the Battle did occur in 1066. After all, had Jean been mistaught that the Battle occurred in 1066, and had he forgotten being ‘taught’ this and subsequently ‘guessed’ that it took place in 10690, we would surely describe the situation as one in which Jean’ false belief about te Battle became a memory trace that was causally responsible or his guess. Thus while Jean consciously believes that the Battle did not occur in 1066, unconsciously he does believe it occurred in 1066. So after all, Radford does not have a counterexample to the claim that knowledge entails belief.
Suppose that Jean’s memory had been sufficiently powerful to produce the relevant belief. As Radford says, Jan has every reason to suppose that his response is mere guesswork, and so he has every reason to consider his belief false. His belief would be an irrational one, and hence one about whose truth Jean would be ignorant.
The attempt to understand the concepts involved in religious belief, existence, necessity, fate, creation, sun, justice, Mercy, Redemption, God. Until the 20th century the history of western philosophy is closely intertwined with attempts to make sense of aspect of pagan, Jewish or Christian religion, while in other tradition such as Hinduism, Buddhism or Taoism, there is even less distinction between religious and philosophical enquiry. The classic problem of conceiving an appropriate object of religious belief is that of understanding whether any term can be predicated of it: Does it make to any sense of talking about its creating to things, willing event, or being one thing or many? The via negativa of theology is to claim that God can only be known by denying ordinary terms of any application (or them); another influential suggestion is that ordinary term only apply metaphorically, sand that there is in hope of cashing the metaphors. Once a description of a Supreme Being is hit upon, there remains the problem of providing any reason for supposing that anything answering to the description exists. The medieval period was the high-water mark-for purported proofs of the existence of God, such as the Five-Ays of Aquinas, or the ontological argument of such proofs have fallen out of general favour since the 18th century, although theories still sway many people and some philosophers.
Generally speaking, even religious philosophers (or perhaps, they especially) have been wary of popular manifestations of religion. Kant, himself a friend of religious faith, nevertheless distinguishes various perversions: Theosophy (using transcendental conceptions that confuses reason), demonology (indulging an anthropomorphic, mode of representing the Supreme Being), theurgy (a fanatical delusion that feeling can be communicated from such a being, or that we can exert an influence on it), and idolatry, or a superstition’s delusion the one can make oneself acceptable to his Supreme Being by order by means than that of having the moral law at heart (Critique of judgement) these warm conversational tendencies have, however, been increasingly important in modern theology.
Since Feuerbach there has been a growing tendency for philosophy of religion either to concentrate upon the social and anthropological dimension of religious belief, or to treat a manifestation of various explicable psychological urges. Another reaction is retreat into a celebration of purely subjective existential commitments. Still, the ontological arguments continue to attach attention. A modern anti-fundamentalists trends in epistemology are not entirely hostile to cognitive claims based on religious experience.
Still, the problem f reconciling the subjective or psychological nature of mental life with its objective and logical content preoccupied from of which is next of the problem was elephantine Logische untersuchungen (trans. as Logical Investigations, 1070). To keep a subjective and a naturalistic approach to knowledge together. Abandoning the naturalism in favour of a kind of transcendental idealism. The precise nature of his change is disguised by a pechant for new and impenetrable terminology, but the ‘bracketing’ of eternal questions for which are to a great extent acknowledged implications of a solipistic, disembodied Cartesian ego s its starting-point, with it thought of as inessential that the thinking subject is ether embodied or surrounded by others. However by the time of Cartesian Meditations (trans. as, 1960, fist published in French as Méditations Carthusianness, 1931), a shift in priorities has begun, with the embodied individual, surrounded by others, than the disembodied Cartesian ego now returned to a fundamental position. The extent to which the desirable shift undermines the programme of phenomenology that is closely identical with Husserl’s earlier approach remains unclear, until later phenomenologists such as Merleau -Ponty has worked fruitfully from the later standpoint.
Pythagoras established and was the central figure in school of philosophy, religion, and mathematics: He was apparently viewed by his followers as semi-divine. For his followers the regular solids (symmetrical three-dimensional forms in which all sides are the same regular polygon) with ordinary language. The language of mathematical and geometric forms seem closed, precise and pure. Providing one understood the axioms and notations, and the meaning conveyed was invariant from one mind to another. The Pythagoreans following which was the language empowering the mind to leap beyond the confusion of sense experience into the realm of immutable and eternal essences. This mystical insight made Pythagoras the figure from antiquity must revered by the creators of classical physics, and it continues to have great appeal for contemporary physicists as they struggle with the epistemological of the quantum mechanical description of nature.
Pythagoras (570 Bc) was the son of Mn esarchus of Samos ut, emigrated (531 Bc) to Croton in southern Italy. Here he founded a religious society, but were forces into exile and died at Metapomtum. Membership of the society entailed self-disciplined, silence and the observance of his taboos, especially against eating flesh and beans. Pythagoras taught the doctrine of metempsychosis or te cycle of reincarnation, and was supposed ale to remember former existence. The soul, which as its own divinity and may have existed as an animal or plant, can, however gain release by a religious dedication to study, after which it may rejoin the universal world-soul. Pythagoras is usually, but doubtfully, accredited with having discovered the basis of acoustics, the numerical ratios underlying the musical scale, thereby y intimating the arithmetical interpretation of nature. This tremendous success inspired the view that the whole of the cosmos should be explicable in terms of harmonia or number. the view represents a magnificent brake from the Milesian attempt to ground physics on a conception shared by all things, and to concentrate instead on form, meaning that physical nature receives an intelligible grounding in different geometric breaks. The view is vulgarized in the doctrine usually attributed to Pythagoras, that all things are number. However, the association of abstract qualitites with numbers, but reached remarkable heights, with occult attachments for instance, between justice and the number four, and mystical significance, especially of the number ten, cosmologically Pythagoras explained the origin of the universe in mathematical terms, as the imposition of limit on the limitless by a kind of injection of a unit. Followers of Pythagoras included Philolaus, the earliest cosmosologist known to have understood that the earth is a moving planet. It is also likely that the Pythagoreans discovered the irrationality of the square root of two.
The Pythagoreans considered numbers to be among te building blocks of the universe. In fact, one of the most central of the beliefs of Pythagoras mathematihoi, his inner circle, was that reality was mathematical in nature. This made numbers valuable tools, and over time even the knowledge of a number’s name came to be associated with power. If you could name something you had a degree of control over it, and to have power over the numbers was to have power over nature.
One, for example, stood for the mind, emphasizing its Oneness. Two was opinion, taking a step away from the singularity of mind. Three was wholeness (a whole needs a beginning, a middle and its ending to be more than a one-dimensional point), and four represented the stable squareness of justice. Five was marriage-being the sum of three and two, the first odd (male) and even (female) numbers. (Three was the first odd number because the number one was considered by the Greeks to be so special that it could not form part of an ordinary grouping of numbers).
The allocation of interpretations went on up to ten, which for the Pythagoreans was the number of perfections. Not only was it the sum of the first four numbers, but when a series of ten dots are arranged in the sequence 1, 2, 3, 4, . . . each above the next, it forms a perfect triangle, the simplest of the two-dimensional shapes. So convinced were the Pythagoreans of the importance of ten that they assumed there had to be a tenth body in the heavens on top of the known ones, an anti-Earth, never seen as it was constantly behind the Sun. This power of the number ten, may also have linked with ancient Jewish thought, where it appears in a number of guised the ten commandments, and the ten the components are of the Jewish mystical cabbala tradition.
Such numerology, ascribed a natural or supernatural significance to number, can also be seen in Christian works, and continued in some new-age tradition. In the Opus majus, written in 1266, the English scientist-friar Roger Bacon wrote that: ‘Moreover, although a manifold perfection of number is found according to which ten is said to be perfect, and seven, and six, yet most of all does three claim itself perfection’.
Ten, we have already seen, was allocated to perfection. Seven was the number of planets according to the ancient Greeks, while the Pythagoreans had designated the number as the universe. Six also has a mathematical significance, as Bacon points out, because if you break it down into te factor that can be multiplied together to make it-one, two, and three-they also add up to six:
1 x 2 x 3 = 6 = 1 + 2 + 3
Such was the concern of the Pythagoreans to keep irrational numbers to themselves, bearing in mind, it might seem amazing that the Pythagoreans could cope with the values involved in this discovery. After all, as the square root of 2 cannot be represented by a ratio, we have to use a decimal fraction to write it out. It would be amazing, were it true that the Greeks did have a grasp for the existence of irrational numbers as a fraction. In fact, though you might find it mentioned that the Pythagoreans did, to talk about them understanding numbers in its way, totally misrepresented the way they thought.
At this point, as occupied of a particular place in space, and giving the opportunity that our view presently becomes fused with Christian doctrine when logos are God’s instrument in the development (redemption) of the world. The notion survives in the idea of laws of nature, if these conceived of as independent guides of the natural course of events, existing beyond the temporal world that they order. The theory of knowledge and its central questions include the origin of knowledge, the place of experience in generating knowledge, and the place of reason in doing so, the relationship between knowledge and certainty, not between knowledge and the impossibility of error, the possibility of universal scepticism, sand the changing forms of knowledge that arise from new conceptualizations of the world and its surrounding surfaces.
As, anyone group of problems concerns the relation between mental and physical properties. Collectively they are called ‘the mind-body problem ‘ this problem is of its central questioning of philosophy of mind since Descartes formulated in the three centuries past, for many people understanding the place of mind in nature is the greatest philosophical problem. Mind is often thought to be the last domain that stubbornly resists scientific understanding, and philosophers differ over whether they find that a cause for celebration or scandal, the mind-body problem in the modern era was given its definitive shape by Descartes, although the dualism that he espoused is far more widespread and far older, occurring in some form wherever there is a religious or philosophical tradition by which the soul may have an existence apart from the body. While most modern philosophers of mind would reject the imaginings that lead us to think that this makes sense, there is no consensus over the way to integrate our understanding people a bearer s of physical proper ties on the one hand and as subjects of mental lives on the other.
As the motivated convictions that discoveries of non-locality have more potential to transform our conceptions of the ‘way things are’ than any previous discovery, it is, nonetheless, that these implications extend well beyond the domain of the physical sciences, and the best efforts of many thoughtful people will be required to understand them.
Perhaps the most startling and potentially revolutionary of these implications in human terms is the view in the relationship between mind and world that is utterly different from that sanctioned by classical physics. René Descartes, for reasons of the moment, was among the first to realize that mind or consciousness in the mechanistic world-view of classical physics appeared to exist in a realm separate and the distinction drawn upon ‘self-realisation’ and ‘undivided wholeness’ he lf within the form of nature. Philosophy quickly realized that there was nothing in this view of nature that could explain or provide a foundation for the mental, or for all that we know from direct experience and distinctly human. In a mechanistic universe, he said, there is no privileged place or function for mind, and the separation between mind and matter is absolute. Descartes was also convinced, however, that the immaterial essences that gave form and structure to this universe were coded in geometrical and mathematical ideas, and this insight led him to invent algebraic geometry.
Decanters’ theory of knowledge starts with the quest for certainty, for an indubitable starting-point or foundation on the basis alone of which progress is possible, sometimes known as the use of hyperbolic (extreme) doubt, or Cartesian doubt. This is the method of investigating how much knowledge and its basis in reason or experience used by Descartes in the first two Meditations. This is eventually found in the celebrated ‘Cogito ergo sum’: I think therefore I am. By finding the point of certainty in my own awareness of my own self, Descartes gives a first-person twist to the theory of knowledge that dominated the following centuries in spite of various counter attacks for social and public starting-point. The metaphysic associated with this priority is the famous Cartesian dualism, or separation of mind and matter into two different but interacting substances. Descartes rigorously and rightly understands the presence of divine dispensation to certify any relationship between the two realms thus divided, and to prove the reliability of the senses invoked a ‘clear and distinct perception’ of highly dubious proofs of the existence of a benevolent deity. This has not met general acceptance: As Hume drily puts it, ‘to have recourse to the veracity of the supreme Being, to prove the veracity of our senses, is surely making a very unexpected circuit.’
In his own time Descartes’s conception of the entirely separate substance of the mind was recognized to precede to insoluble problems of nature of the causal connection between the two systems running in parallel. When I stub my toe, this does not cause pain, but there is a harmony between the mental and the physical (perhaps, due to God) that ensure that there will be a simultaneous pain; when I form an intention and then act, the same benevolence ensures that my action is appropriate to my intention, or if it be to desire its resultant intention be of an action to be performed on the causal effect of some unreasonable belief. The theory has never been wildly popular, and in its application to mind-body problems many philosophers would say that it was the result of a misconceived ‘Cartesian dualism,’ it of ‘subjective knowledge’ and ‘physical theory.’
It also produces the problem, insoluble in its own terms, of ‘other minds.’ Descartes’s notorious denial that nonhuman animals are conscious is a stark illustration of the problem. In his conception of matter Descartes also gives preference to rational cogitation over anything derived from the senses. Since we can conceive of the matter of a ball of wax surviving changes to its sensible qualities, matter is not an empirical concept, but eventually an entirely geometrical one, with extension and motion as its only physical nature. Descartes’ s thought is reflected in Leibniz’s view, held later by Russell, that the qualities of sense experience have no resemblance to qualities of things, so that knowledge of the external world is essentially knowledge of structure than of filling. On this basis Descartes builds a remarkable physics. Since matter is in effect the same as extension there can be no empty space or ‘void,’ since there is no empty space motion is not a question of occupying previously empty space, but is to be thought of through vortices (like the motion of a liquid).
Although the structure of Descartes’s epistemology, theory of mind, and theory of matter have been rejected often, their relentless exposures of the hardest issues, their exemplary clarity, and even their initial plausibility, all contrive to make him the central point of reference for modern philosophy.
A scientific understanding of these ideas could be derived, said, Descartes, with the aid of precise deduction, and has also claimed that the contours of physical reality could be laid out in three-dimensional coordinates. Following the publication of Isaac Newton’s Principia Mathematica in 1687, reductionism and mathematical modelling became the most powerful tools of modern science. The dream that the entire physical world could be known and mastered through the extension and refinement of mathematical theory became the central feature and principle of scientific knowledge.
Nevertherless, the 19th-century German philosopher Friedrich Nietzsche further contended that the individual must decide which situations are to count as moral situations.
Germany appeared to have invaded vast territories of the world’s mind, with Nietzsche himself as no mean conqueror. For his was the vision of things to come. Much, too much, would strike him as déjà vu: Yes, he had foreseen it, and he would understand, for the ‘Modern Mind’ speaks German, not always good German, but fluent German nonetheless, it was, only forced by learning the idiom of Karl Marx, and was delighted to be introduced to itself in the language of Sigmund Freud’ taught by Rank and later Max Weber, It acquired its historical and sociological self-consciousness, moved out of its tidy Newtonian universe on the instruction of Einstein, and followed a design of Oswald Spengler’s in sending, from the depth of its spiritual depression, most ingeniously engineered objects higher than the moon. Whether it discovers, with Heidegger, the true habitation of its Existenza on the frontier boundaries of Nothing, or mediates, with Sartre and Camus le Néant or the Absurd, whether - to pass to its less serous moods - it is nihilistically young and profitably angry in London or rebelliously debauched and Buddhistic in San Francisco - it is part of a story told by Nietzsche.
As for modern German literature and thought, it is hardly an exaggeration to say that they would not be what they are if Nietzsche had never lived. Name almost any poet, man of letters, philosopher, who wrote in German during the twentieth century and attained to stature and influence - Rilke, George, Kafka, Tomas Mann, Ernst Jünger, Musil, Benn, Heidegger, or Jaspers - and you name at the same time Friedrick Nietzsche. He is too, them all - whether or not they know and acknowledge it (most of them do) - what St. Thomas Aquinas was to Dante: The categorical interpreter of a world that they contemplate poetically or philosophically without ever radically upsetting its Nietzschean structure.
He was convinced that it would take at least fifty years before a few men would understand what he had accomplished. He feared that even then his teaching would be misinterpreted and misapplied. “I am terrified,” he wrote, “by the thought of the sort of people who may one day invoke my authority.” Yet is this not, he added, the anguish of every great teacher? Still, the conviction that he was a great teacher never left him after he had passed through that period of sustained inspiration in which he wrote the first part of Zarathustra. After this, all his utterances convey the disquieting self-confidence and the terror of a man who has reached the culmination of that paradox that he embodies, and whichever has since cast its dangerous spell over some of the finest and some of the coarsest minds.
Are we then, in a better position to probe Nietzsche’s mind and too avid, as he anticipated some might, the misunderstanding that he was merely concerned with religious, philosophical, or political controversies fashionable in his day? If this is a misinterpretation, can we put anything more valid in its place? What is the knowledge that he claims to have, raising him in his own opinion far above the contemporary level of thought? What the discovery that serves him as a lever to unhinge the whole fabric of traditional values?
It is the knowledge that God is dead.
The death of God he calls the greatest event in modern history and the cause of extreme danger. Its paradoxical place a value may be contained in these words. He never said that there was no God, but that the External had been vanquished by Time and that the immortal suffered death at the hands of mortals: “God is dead.” It is like a cry mingled of despair and triumph, reducing, by comparison, the whole story of atheism and agnosticism before and after him to the level of respectable mediocrity and making it sound like a collection of announcements by bankers who regret they are unable to invest in an unsafe proposition. Nietzsche, for the nineteenth century, brings to its perverse conclusion a line of religious thought and experience linked with the names of St. Paul, St. Augustine, Pascal, Kierkegaard, and Dostoevsky, minds for whom God has his clearly defined place, but to whom. He came in order to challenge their natural being, making demands that appeared absurd in the light of natural reason. These men are of the family of Jacob: Having wrestled with God for His blessing, they ever after limp through life with the framework of Nature incurably out of joint. Nietzsche too believed that he prevailed against God in that struggle, and won a new name for himself, the name of Zarathustra. However, the words he spoke on his mountain to the angel of the Lord? I will not let thee go, but thou curse me. Or, in words that Nietzsche did in fact speak: “I have on purpose devoted my life to exploring the whole contrast to a truly religious nature. I know the Devil and all his visions of God.
“God is dead” - this is the very core of Nietzsche’s spiritual existence, and what follows is despair and hope in a new greatness of man, visions of catastrophe and glory, the icy brilliance of analytical reason, fathoming with affected irreverence those depths through which are hidden of a ritual healer.
Perhaps by definition alone, comes the unswerving call of atheism, by this is the denial of or lack of belief in the existence of a god or gods. The term atheism comes from the Greek prefix ‘a-‘, meaning “without,” and the Greek word ‘theos’, meaning “deity.” The denial of gods’ existence is also known as strong, or positive, atheism, whereas the lack of belief in a god is known as negative, or weak, atheism. Although atheism is often contrasted with agnosticism - the view that we cannot know whether a deity exists or not and should therefore suspend belief - negative atheism is in fact compatible with agnosticism.
About one-third of the world’s population adheres to a form of Christianity. Latin America has the largest number of Christians, most of whom are Roman Catholics. Islam is practised by over one-fifth of the world’s population, most of whom live in parts of Asia, particularly the Middle East.
Atheism has wide-ranging implications for the human condition. In the rendering absence to belief in a god, as, too, ethical goals must be determined by secular and nonreligious aims of concern, human beings must take full responsibility for their destiny, and death marks the end of a person’s existence. As of 1994 there were an estimated 240 million atheists around the world comprising slightly more than 4 percent of the world’s population, including those who profess atheism, skepticism, disbelief, or irreligion. The estimate of nonbelievers increases significantly, to about 21 percent of the world’s population, if negative atheists are included.
From ancient times, people have at times used atheism as a term of abuse for religious positions they opposed. The first Christians were called atheists because they denied the existence of the Roman deities. Over time, several misunderstandings of atheism have arisen: That atheists are immoral, that morality cannot be justified without belief in God, and that life has no purpose without belief in God. Yet there is no evidence that atheists are any less moral than believers. Many systems of morality have been developed that do not presuppose the existence of a supernatural being. Moreover, the purpose of human life may be based on secular goals, such as the betterment of humankind.
In Western society the term atheism has been used more narrowly to refer to the denial of theism, in particular Judeo-Christian theism, which asserts the existence of an all-powerful, all-knowing, all-good personal being. This being created the universe, took an active interest in human concerns, and guides his creatures through divine disclosure known as revelation. Positive atheists reject this theistic God and the associated beliefs in an afterlife, a cosmic destiny, a supernatural origin of the universe, an immortal soul, the revealed nature of the Bible and the Qur'an (Koran), and a religious foundation for morality.
Theism, however, is not a characteristic of all religions. Some religions reject theism but are not entirely atheistic. Although the theistic tradition is fully developed in the Bhagavad-Gita, the sacred text of Hinduism, earlier Hindu writings known as the Upanishads teach that Brahman (ultimate reality) is impersonal. Positive atheists reject even the pantheistic aspects of Hinduism that equate God with the universe. Several other Eastern religions, including Theravada Buddhism and Jainism, are commonly believed to be atheistic, but this interpretation is not strictly correct. These religions do reject a theistic God believed to have created the universe, but they accept numerous lesser gods. At most, such religions are atheistic in the narrow sense of rejecting theism.
One of the most controversial works of 19th-century philosophy, Thus Spake Zarathustra 1883-1885, articulated German philosopher Friedrich Nietzsche’s theory of the Übermensch, a term translated as “Superman” or “Overman.” The Superman was an individual who overcame what Nietzsche termed the “slave morality” of traditional values, and lived according to his own morality. Nietzsche also advanced his idea that “God is dead,” or that traditional morality was no longer relevant in people’s lives. In this passage, the sage Zarathustra came down from the mountain where he had spent the last ten years alone to preach to the people.
In the Western intellectual world, nonbelief in the existence of God is a widespread phenomenon with a long and distinguished history. Philosophers of the ancient world such as Lucretius were nonbelievers. Even in the Middle Ages (5th to 15th centuries) there were currents of thought that questioned theist assumptions, including skepticism, the doctrine that true knowledge is impossible, and naturalism, the belief that only natural forces control the world. Several leading thinkers of the Enlightenment (1700-1789) were professed atheists, including Danish writer Baron Holbach and French encyclopedist Denis Diderot. Expressions of nonbelief also are found in classics of Western literature, including the writings of English poets Percy Shelley and Lord Byron, the English novelist Thomas Hardy, including French philosophers’ Voltaire and Jean-Paul Sartre, the Russian author Ivan Turgenev, and the American writers’ Mark Twain and Upton Sinclair. In the 19th century the most articulate and best-known atheists and critics of religion were German philosophers’ Ludwig Feuerbach, Karl Marx, Arthur Schopenhauer, and Friedrich Nietzsche. British philosopher Bertrand Russell, Austrian psychoanalyst Sigmund Freud, and Sartre are among the 20th century’s most influential atheists.
Nineteenth-century German philosopher Friedrich Nietzsche was an influential critic of religious systems, especially Christianity, for which he felt chained to the thickening herd morality. By declaring that “God is dead,” Nietzsche signified that traditional religious belief in God no longer played a central role in human experience. Nietzsche believed we would have to find secular justifications for morality to avoid nihilism - the absence of all belief.
Atheists justify their philosophical position in several different ways. Negative atheists attempt to establish their position by refuting typical theist arguments for the existence of God, such as the argument from first cause, the argument from design, the ontological argument, and the argument from religious experience. Other negative atheists assert that any statement about God is meaningless, because attributes such as all-knowing and all-powerful cannot be comprehended by the human mind. Positive atheists, on the other hand, defend their position by arguing that the concept of God is inconsistent. They question, for example, whether a God who is all-knowing can also be all-good and how a God who lacks bodily existence can be all-knowing.
Some positive atheists have maintained that the existence of evil makes the existence of God improbable. In particular, atheists assert that theism does not provide an adequate explanation for the existence of seemingly gratuitous evil, such as the suffering of innocent children. Theists commonly defend the existence of evil by claiming that God desires that human beings have the freedom to choose between good and evil, or that the purpose of evil is to build human character, such as the ability to persevere. Positive atheists counter that justifications for evil in terms of human free will leave unexplained why, for example, children suffer because of genetic diseases or abuse from adults. Arguments that God allows pain and suffering to build human character fail, in turn, to explain why there was suffering among animals before human beings evolved and why human character could not be developed with less suffering than occurs in the world. For atheists, a better explanation for the presence of evil in the world is that God does not exist.
Atheists have also criticized historical evidence used to support belief in the major theistic religions. For example, atheists have argued that a lack of evidence casts doubt on important doctrines of Christianity, such as the virgin birth and the resurrection of Jesus Christ. Because such events are said to represent miracles, atheists assert that extremely strong evidence is necessary to support their occurrence. According to atheists, the available evidence to support these alleged miracles - from Biblical, pagan, and Jewish sources - is weak, and therefore such claims should be rejected.
Atheism is primarily a reaction to, or a rejection of, religious belief, and thus does not determine other philosophical beliefs. Atheism has sometimes been associated with the philosophical ideas of materialism, which holds that only matter exists. Communism, which asserts that religion impedes human progress, and rationalism, which emphasizes analytic reasoning over other sources of knowledge. However, there is no necessary connection between atheism and these positions. Some atheists have opposed communism and some have rejected materialism. Although nearly all contemporary materialists are atheists, the ancient Greek materialist Epicurus believed the gods were made of matter in the form of atoms. Rationalists such as French philosopher René Descartes have believed in God, whereas atheists such as Sartre are not considered to be rationalists. Atheism has also been associated with systems of thought that reject authority, such as anarchism, a political theory opposed to all forms of government, and existentialism, a philosophic movement that emphasizes absolute human freedom of choice; there is however no necessary connection between atheism and these positions. British analytic philosopher A.J. Ayer was an atheist who opposed existentialism, while Danish philosopher Søren Kierkegaard was an existentialist who accepted God. Marx was an atheist who rejected anarchism while Russian novelist Leo Tolstoy, a Christian, embraced anarchism. Because atheism in a strict sense is merely a negation, it does not provide a comprehensive world-view. Presuming other philosophical positions to be outgrowths of atheism is therefore not possible.
Intellectual debate over the existence of God continues to be active, especially on college campuses, in religious discussion groups, and in electronic forums on the Internet. In contemporary philosophical thought, atheism has been defended by British philosopher Antony Flew, Australian philosopher John Mackie, and American philosopher Michael Martin, among others. Leading organizations of unbelief in the United States include The American Atheists, The Committee for the Scientific Study of Religion.
Friedrich Nietzsche (1844-1900), German philosopher, poet, and classical philologist, who was one of the most provocative and influential thinkers of the 19th century. Nietzsche founded his morality on what he saw as the most basic human drive, the will to power. Nietzsche criticized Christianity and other philosophers’ moral systems as “slave moralities” because, in his view, they chained all members of society with universal rules of ethics. Nietzsche offered, in contrast, a “master morality” that prized the creative influence of powerful individuals who transcended the common rules of society.
Nietzsche studied classical philology at the universities of Bonn and Leipzig and was appointed the professor of classical philology at the University of Basel at the age of 24. Ill health (he was plagued throughout his life by poor eyesight and migraine headaches) forced his retirement in 1879. Ten years later he suffered a mental breakdown from which he never recovered. He died in Weimar in 1900.
In addition to the influence of Greek culture, particularly the philosophies of Plato and Aristotle, Nietzsche was influenced by German philosopher Arthur Schopenhauer, by the theory of evolution, and by his friendship with German composer Richard Wagner.
Nietzsche’s first major work, Die Geburt der Tragödie aus dem Geiste de Musik (The Birth of Tragedy), appeared in 1872. His most prolific period as an author was the 1880s. During the decade he wrote, Also sprach Zarathustra (Parts one-3, 1883-1884; Part four-4, 1885, and translated to English as, Thus Spake Zarathustra), Jenseits von Gut und Böse, 1886, Beyond Good and Evil - Zur Genealogie de Moral, 1887, also, On the Genealogy of Morals, and the German, Der Antichrist 1888, the English translation, The Antichrist, and Ecce Homo, was completed 1888, and published 1908. Nietzsche’s last major work, The Will to Power, Der Wille zur Macht, was published in 1901.
One of Nietzsche’s fundamental contentions was that traditional value (represented primarily by Christianity) had lost their power in the lives of individuals. He expressed this in his proclamation “God is dead.” He was convinced that traditional values represented a “slave morality,” a morality created by weak and resentful individuals who encouraged such behaviour as gentleness and kindness because the behaviour served their interests. Nietzsche claimed that new values could be created to replace the traditional ones, and his discussion of the possibility led to his concept of the overman or superman.
According to Nietzsche, the masses (whom he termed the herd or mob) conform to tradition, whereas his ideal overman is secure, independent, and highly individualistic. The overman feels deeply, but his passions are rationally controlled. Concentrating on the real world, than on the rewards of the next world promised by religion, the overman affirms life, including the suffering and pain that accompany human existence. Nietzsche’s overman is a creator of values, a creator of its “master morality” that reflects the strength and independence of one who is liberated from all values, except those that he deems valid.
Nietzsche maintained that all human behaviour is motivated by the will to power. In its positive sense, the will to power is not simply power over others, but the power over one’s self that is necessary for creativity. Such power is manifested in the overman's independence, creativity, and originality. Although Nietzsche explicitly denied that any overmen had yet arisen, he mentions several individuals who could serve as models. Among these models he lists Jesus, Greek philosopher Socrates, Florentine thinker Leonardo da Vinci, Italian artist Michelangelo, English playwright William Shakespeare, German author Johann Wolfgang von Goethe, Roman ruler Julius Caesar, and French emperor Napoleon I.
The concept of the overman has often been interpreted as one that postulates a master-slave society and has been identified with totalitarian philosophies. Many scholars deny the connection and attribute it to misinterpretation of Nietzsche's work.
An acclaimed poet, Nietzsche exerted much influence on German literature, as well as on French literature and theology. His concepts have been discussed and elaborated upon by such individuals as German philosophers Karl Jaspers and Martin Heidegger, and German Jewish philosopher Martin Buber, German American theologian Paul Tillich, and French writers’ Albert Camus and Jean-Paul Sartre. After World War II (1939-1945), American theologians’ Thomas J.J. Altizer and Paul Van Buren seized upon Nietzsche's proclamation “God is dead” in their attempt to make Christianity relevant to its believers in the 1960s and 1970s.
Nietzsche is openly pessimistic about the possibility of knowledge, for truth: we know (or, believe or imagine) just as much as may be useful in the interests of the human herd, the species: and even what is here called ‘utility’, is ultimately also a mere belief, something imaginary and perhaps precisely that most calamitous stupidity of which we shall perish some day.
This position is very radical. Nietzsche does not simply deny that knowledge, construed as the adequate representation of the world by the intellect, exists. He also refuses the pragmatist identification of knowledge and truth with usefulness: he writes that we think we know what we think is useful, and that we can be quite wrong about the latter.
Nietzsche’s view, his ‘perspectivism’, depends on his claim that there is no sensible conception of a world independent of human interpretation and to which interpretations would correspond if they were to constitute knowledge. He sums up this highly controversial position in The Will to Power: Facts are precisely what there is not, only interpretation.
It is often claimed that perspectivism is self-undermining, if the thesis that all views are interpretations is true then, it is argued, there is at least one view that is not an interpretation. If, on the other hand, the thesis is itself an interpretation, then there is no reason to believe that it is true, and it follows again, that not every view is an interpretation.
Nevertheless, this refutation assumes that if a view of perspectivism itself, is an interpretation that it is wrong. This is not the case, to call any view, including perspectivism. An interpretation is to say that it can be wrong, which is true of all views, and that is not a sufficient refutation. To show the perspectivism is actually false producing another view superior to it on specific epistemological grounds is necessary.
Perspectivism does not deny that particular views can be true. Like some versions of contemporary anti-realism, only by its attributes to specific approaches’ truth in relation to facts specified internally by the approaches themselves. Nonetheless, it refuses to envisage a single independent set of facts, to be accounted for by all theories. Thus Nietzsche grants the truth of specific scientific theories, he does, nevertheless, deny that a scientific interpretation can possibly be ‘the only justifiable interpretation of the world’, neither the fact’s science addresses nor the methods it employs are privileged. Scientific theories serve the purpose for which they have been devised, but these have no priority over the many other purposes of human life.
The existence of many purposes and needs relative to which the value of theories is established - another crucial element of perspectivism - is sometimes thought to imply a lawless relativism. According to which no standards for evaluating purposes and theories can be devised. This is correct only in that Nietzsche denies the existence of a single set of standards for determining epistemic value once and for all. However, he holds that specific views can be compared with and evaluated in relation to one another. The ability to use criteria acceptable in particular circumstances does not presuppose the existence of criteria applicable in all. Agreement is therefore, not always possible, since individuals may sometimes differ over the most fundamental issues dividing them.
Least of mention, Nietzsche would not be troubled by this fact, which his opponents too also have to confront only, as he would argue, to suppress it by insisting on the hope that all disagreements are in principal eliminable even if our practice falls woefully short of the ideal. Nietzsche abandons that ideal. He considers irresoluble disagreement an essential parts of human life.
Since, scientists during the nineteenth century were preoccupied with uncovering the workings of external reality and virtually nothing was known about the physical substrate is of human consciousness, the business of examining the dynamics and structure of mind became the province of ‘social scientists’ and ‘humanists’. Adolphe Quételet proposed a social physics’ that could serve as the basis for a new discipline called sociology, and his contemporary Auguste Comte concluded that a true scientific understanding of the social reality was quite inevitable. Mind, in the view of these figures, was a separate and distinct mechanism subject to the lawful workings of a mechanistic social reality.
More formal European philosophers, such as Immanuel Kant, sought to reconcile representations of external reality in mind with the motions of matter based on the dictates of pure reason. This impulse was also apparent in the utilitarian ethics of Jeremy Bentham and John Stuart Mill, in the historical materialist of Karl Marx and Friedrich Engels, and in the pragmatism of Charles Smith, William James, and John Dewey. All these thinkers were painfully aware, however, of the inability of reason to posit a self-consistent basis for bridging the gap between mind and matter, and each was obligated to conclude that the realm of the mental exists only in the subjective reality of the individual.
The fatal flaw of pure reason is, of course, the absence of emotion, and purely rational explanations of the division between subjective reality and external reality had limited appeal outside the community of intellectuals, the figure most responsible for infusing our understanding of Cartesian dualism with emotional content was the death of God theologian Friedrich Nietzsche. After declaring that God and ‘divine will’, did not exist, Nietzsche reified the ‘existence’ of consciousness in the domain of subjectivity as the ground for individual ‘will’ and summarily dismissed all previous philosophical attempts to articulate the ‘will to truth’. The problem, claimed Nietzsche, is that linear versions of the ‘will to truth’ disguise the fact that all alleged truths were arbitrarily created in the subjective reality of the individual and are expressions or manifestations of individual ‘will’.
Nietzsche’s emotionally charged defence of intellectual freedom and his radical empowerment of mind as the maker and transformer of the collective fictions that shape human reality in a soulless mechanistic universe proved terribly influential on twentieth-century thought. Nietzsche sought to reinforce his view of the subjective character of scientific knowledge and arithmetic that arose during the last three decades of the nineteenth century. Though a curious course of events, attempts by Edmund Husserl, a philosopher trained in higher math and physics, to resolve this crisis results in a view of the character of human consciousness that closely resembled that of Nietzsche.
The best-known disciple of Husserl was Martin Heidegger, and the work of both figures greatly influenced that of the French atheistic existenualist Jean-Paul Sartre. The work of Husserl, Heidegger, and Sartre became foundational to that of the principal architects of philosophical postmodernism, the deconstructionalists Jacques Lacan, Roland Barthes, Michel Foucault, and Jacques Derrida, this direct line found linkage between the nineteenth-century crisis about the epistemological foundations of mathematical physics and the origins of philosophical postmodernism served to perpetuate the Cartesian two world dilemma, in, an even, or oppressive form.
Philosophers like John Locke, Thomas Hobbes, and David Hume tried to articulate some basis for liking the mathematical describable motions of matter with linguistic representations of external reality in the subjective space of mind. Descartes’ compatriot Jean-Jacques Rousseau reified nature as the ground of human consciousness in a state of innocence and proclaimed that ‘Liberty, Equality, Fraternity’ is the guiding principles of this consciousness. Rousseau also made god-like the idea of the ‘general will’ of the people to achieve these goals and declared that those who do not conform to this will were social deviants.
The Enlightenment idea of deism, which imagined the universe as a clockwork and God as the clockmaker, provided grounds for believing in a divine agency lay the moment of creation. It also implied, however, that all the creative forces of the universe were exhausted at origins, that the physical substrates of mind were subject to the same natural laws as matter, and that the only means of mediating the gap between mind and matter was pure reason. Traditional Judeo-Christian theism, which had previously been based on both reason and revelation, responded to the challenge of deism by debasing rationality as a test of faith and embracing the idea that the truth of spiritual reality can be known only through divine revelation. This engendered a conflict between reason and revelation that persists to this day. And it also laid the fundamental for the fierce competition between the mega-narratives of science and religion as frame tale s for mediating the character of each should be ultimately defined.
The most fundamental aspect of intellectual tradition is the assumption that there is a fundamental division between the material and the immaterial world or between the realm of matter and the realm of pure mind and spirit. The metaphysical framework based on this assumption known as ontological dualism. As the word dual implies, the framework is predicated on an ontology, or a conception of the nature of God or Being, that assumes reality has two distinct and separable dimensions. The concept of Being as continuous, immutable, and having a prior or separate existence from the world of change dates from the ancient Greek philosopher Parmenides. The same qualities were associated with the God of the Judeo-Christian tradition, and they were considerably amplified by the role played in the theology by Platonic and Neoplatonic philosophy.
The role of seventeenth-century metaphysics is also apparent in metaphysical presuppositions about matter described by classical enumerations of motion. These presuppositions can be briefly defined as follows: (1) The physical world is made up of inert and changeless matter, and this matter changed only in terms of location in space, (2) the behaviour of matter mirrors physical theory and is inherently mathematical, (3) matter as the unchanging unit of physical reality can be exhaustively understood by mechanics, or by the applied mathematics of motion, and (4) the mind of the observer is separate from the observed system of matter, and the ontological bridge between the two physical law and theory.
Once, again, these presuppositions have a metaphysical basis because they are required to assume the following, - that the full and certain truths about the physical world are revealed in a mathematical structure governed by physical laws, which have a prior or separate existence from this world. While Copernicus, Galileo, Kepler, Descartes, and Newton assumed that metaphysics or ontological foundation for these laws was the perfect mind of God, the idea was increasingly regarded, even in the eighteenth century, as somewhat unnecessary, what would endure in an increasingly disguised form was the assumption of ontological dualism. This assumption, which remains alive and well in the debates about scientific epistemology, allowed the truths of mathematical physics to be regarded as having a separate and immutable existence outside the world of change.
As this view of hypotheses and the truths of nature as qualities were extended in the nineteenth century to a mathematical description of phenomena like heat, light, electricity, an magnetism, LaPlaces’ assumptions about the actual character of scientific truths seemed quite correct, this progress suggested that if we could remove all thoughts about the ‘nature of’ or the ‘source of’ phenomena, the pursuit of strictly quantitative concepts would bring us to a complete description of all aspects of physical reality. Subsequently, figures like Combe, Kirchhoff. Hertz, and Poincaré developed a program for the study of nature that was quite different from that of the original creators of classical physics.
The seventeenth-century view of physics as a philosophy of nature or a natural philosophy was displaced by the view of physics as an autonomous science that was ‘the science of nature’. This view, which was premised on the doctrine of positivism, promised to subsume all of the nature with a mathematical analysis of entities in motion and claimed that the true understanding of nature was revealed only in the unmathematical descriptions. Since the doctrine of positivism, assumes that knowledge we call physics resides only in the mathematical formalism of physical theory, it disallows the prospect that the vision of physical reality reveals in physical theory can have any other meaning. In the history of science, the irony is that positivism, which was intended to banish metaphysical concerns from the domain of science, served to perpetuate a seventeenth-century metaphysical assumption about the relationship between physical reality and physical theory.
Kant was to argue that the earlier assumption that our knowledge has the world is a mathematical physics and is wholly determined by the behaviour of physical reality could well be false. Perhaps, he said that the reverse was true - that the objects of nature conform to our knowledge of nature. The relevance of the Kantian position was later affirmed by the leader of the Berlin school of mathematics, Karl Weierstrass, who came to a conclusion that would also be adopted by Einstein - that mathematics is a pure creation of the human mind.
A complete history of the debate over the epistemological foundation of mathematical physics should probably begin with the discovery of irrational numbers by the followers of Pythagoras, the paradoxes of Zeno and Gottfried Leibniz. But since we are more concerned with the epistemological crisis of the late nineteenth century, let us begin with the set theory developed by the German mathematician and logician Georg Cantor. From 1878 to 1897, Cantor created a theory of abstract sets of entities that eventually became a mathematical discipline. A set, as he defined it, is a collection of definite and a distinguishable object in thought or perception conceived as a whole.
Cantor attempted to prove that the proceeds of counting and the definition of integers could be placed on a solid mathematical foundation. His method was repeatedly to place the elements in one set into ‘one-to-one’ correspondence with those in another. In the case of integers, Cantor showed that each integer (1, 2, 3, . . . n) could be paired with an even integer
(2, 4, 6, . . . n), and, therefore, that the set of all integers was equal to the set of all even numbers.
Formidably, Cantor discovered that some infinite sets were larger than others and that infinite sets formed a hierarchy of ever greater infinities. After this failing attempt to save the classical view of logical foundations and internal consistency of mathematical systems, it soon became obvious that a major crack had appeared in the seemingly solid foundations of number and mathematics. Meanwhile, an impressive number of mathematicians began to see that everything from functional analysis to the theory of real numbers depended on the problematic character of number itself.
In 1886, Nietzsche was delighted to learn the classical view of mathematics as a logical consistent and self-contained system that could prove it might be undermined. And his immediate and unwarranted conclusion was that all of logic and the whole of mathematics were nothing more than fictions perpetuated by those who exercised their will to power. With his characteristic sense of certainty, Nietzsche does precisely proclaim. “Without accepting the fictions of logic, without measuring reality against the purely invented world of the unconditional and self-identical, without a constant falsification of the world by means of numbers, man could not live.”
Many writers, along with a few well-known new-age gurus, have played fast and loosely with firm interpretations of some new but informal understanding grounded within the mental in some vague sense of cosmic consciousness. However, these new age nuances are ever so erroneously placed in the new-age section of a commercial bookstore and purchased by those interested in new-age literature, and they will be quite disappointed.
Research in neuroscience has shown that language processing is a staggering complex phenomenon that places incredible demands on memory and learning. Language functions extend, for example, into all major lobes of the neocortex: Auditory opinion is associated with the temporal area; tactile information is associated with the parietal area, and attention, working memory, and planning are associated with the frontal cortex of the left or dominant hemisphere. The left prefrontal region is associated with verb and noun production tasks and in the retrieval of words representing action. Broca’s area, next to the mouth-tongue region of a motor cortex, is associated with vocalization in word formation, and Wernicke’s area, by the auditory cortex, is associated with sound analysis in the sequencing of words.
Lower brain regions, like the cerebellum, have also evolved in our species to help in language processing. Until recently, the cerebellum was thought to be exclusively involved with automatic or preprogrammed movements such as throwing a ball, jumping over a high hurdle or playing noted orchestrations as on a musical instrument. Imaging studies in neuroscience suggest, however, that the cerebellum awaken within the smoldering embers brought aflame by the sparks of awakening consciousness, to think communicatively during the spoken exchange. Mostly actuated when the psychological subject occurs in making difficult the word associations that the cerebellum plays a role in associations by providing access to automatic word sequences and by augmenting rapid shifts in attention.
Critically important to the evolution of enhanced language skills are that behavioural adaptive adjustments that serve to precede and situate biological changes. This represents a reversal of the usual course of evolution where biological change precedes behavioural adaption. When the first hominids began to use stone tools, they probably rendered of a very haphazard fashion, by drawing on their flexible ape-like learning abilities. Still, the use of this technology over time opened a new ecological niche where selective pressures occasioned new adaptions. A tool use became more indispensable for obtaining food and organized social behaviours, mutations that enhanced the use of tools probably functioned as a principal source of selection for both bodied and brains.
The fist stone choppers appear in their fossil executions seem as the remnant fragments remaining about 2.5 million years ago, and they appear to have been fabricated with a few sharp blows of stone on stone. If these primitive tools are reasonable, which were hand-held and probably used to cut flesh and to chip bone to expose the marrow, were created by Homo habilis - the first large-brained hominid. Stone making is obviously a skill passed on from one generation to the next by learning as opposed to a physical trait passed on genetically. After these tools became critical to survival, this introduced selection for learning abilities that did not exist for other species. Although the early tool makers may have had brains roughly comparable to those of modern apes, they were already confronting the processes for being adapted for symbol learning.
The first symbolic representations were probably associated with social adaptations that were quite fragile, and any support that could reinforce these adaptions in the interest of survival would have been favoured by evolution. The expansion of the forebrain in Homo habilis, particularly the prefrontal cortex, was on of the core adaptations. This adaption was enhanced over time by increased connectivity to brain regions involved in language processing.
Imagining why incremental improvements in symbolic representations provided a selective advantage is easy. Symbolic communication probably enhanced cooperation in the relationship of mothers to infants, allowed forgoing techniques to be more easily learned, served as the basis for better coordinating scavenging and hunting activities, and generally improved the prospect of attracting a mate. As the list of domains in which symbolic communication was introduced became longer over time, this probably resulted in new selective pressures that served to make this communication more elaborate. After more functions became dependent on this communication, those who failed in symbol learning or could only use symbols awkwardly were less likely to pass on their genes to subsequent generations.
The crude language of the earliest users of symbolics must have been considerably gestured and nonsymbiotic vocalizations. Their spoken language probably became reactively independent and a closed cooperative system.
The general idea is very powerful, however, the relevance of spatiality to self-consciousness comes about not merely because the world is spatial but also because the self-conscious subject is a spatial element of the world. One cannot be self-conscious without being aware that one is a spatial element of the world, and one cannot be ware that one is a spatial element of the world without a grasp of the spatial nature of the world. Face to face, the idea of a perceivable, objective spatial world that causes ideas too subjectively becoming to denote in the world. During which time, his perceptions as they have of changing position within the world and to the more or less stable way the world is. The idea that there is an objective world and the idea that the subject is somewhere, and where he is given by what he can perceive.
Research, however distant, are those that neuroscience reveals in that the human brain is a massive parallel system which language processing is widely distributed. Computers generated images of human brains engaged in language processing reveals a hierarchal organization consisting of complicated clusters of brain areas that process different component functions in controlled time sequences. And it is now clear that language processing is not accomplished by stand-alone or unitary modules that evolved with the addition of separate modules that were eventually wired together on some neutral circuit board.
While the brain that evolved this capacity was obviously a product of Darwinian evolution, the most critical precondition for the evolution of this brain cannot be simply explained in these terms. Darwinian evolution can explain why the creation of stone tools altered conditions for survival in a new ecological niche in which group living, pair bonding, and more complex social structures were critical to survival. And Darwinian evolution can also explain why selective pressures in this new ecological niche favoured preadaptive changes required for symbolic communication. All the same, this communication resulted directly through its passing an increasingly atypically structural complex and intensively condensed behaviour. Social evolution began to take precedence over physical evolution in the sense that mutations resulting in enhanced social behaviour became selectively advantageously within the context of the social behaviour of hominids.
Because this communication was based on symbolic vocalization that required the evolution of neural mechanisms and processes that did not evolve in any other species. As this marked the emergence of a mental realm that would increasingly appear as separate and distinct from the external material realm.
If the emergent reality in this mental realm cannot be reduced to, or entirely explained as for, the sum of its parts, it seems reasonable to conclude that this reality is greater than the sum of its parts. For example, a complete proceeding of the manner in which light in particular wave lengths has ben advancing by the human brain to generate a particular colour says nothing about the experience of colour. In other words, a complete scientific description of all the mechanisms involved in processing the colour blue does not correspond with the colour blue as perceived in human consciousness. And no scientific description of the physical substrate of a thought or feeling, no matter how accomplish it can but be accounted for in actualized experience, especially of a thought or feeling, as an emergent aspect of global brain function.
If we could, for example, define all of the neural mechanisms involved in generating a particular word symbol, this would reveal nothing about the experience of the word symbol as an idea in human consciousness. Conversely, the experience of the word symbol as an idea would reveal nothing about the neuronal processes involved. And while one mode of understanding the situation necessarily displaces the other, both are required to achieve a complete understanding of the situation.
Even if we are to include two aspects of biological reality, finding to a more complex order in biological reality is associated with the emergence of new wholes that are greater than the orbital parts. Yet, the entire biosphere is of a whole that displays self-regulating behaviour that is greater than the sum of its parts. The emergence of a symbolic universe based on a complex language system could be viewed as another stage in the evolution of more complicated and complex systems. As marked and noted by the appearance of a new profound complementarity in relationships between parts and wholes. This does not allow us to assume that human consciousness was in any sense preordained or predestined by natural process. But it does make it possible, in philosophical terms at least, to argue that this consciousness is an emergent aspect of the self-organizing properties of biological life.
The scientific implications to the relationship between parts (Qualia) and indivisible whole (the universe) are quite staggering. Our primary concern, however, is a new view of the relationship between mind and world that carries even larger implications in human terms. When factors into our understanding of the relationship between parts and wholes in physics and biology, then mind, or human consciousness, must be viewed as an emergent phenomenon in a seamlessly interconnected whole called the cosmos.
All that is required to embrace the alternative view of the relationship between mind and world that are consistent with our most advanced scientific knowledge is a commitment to metaphysical and epistemological realism and a willingness to follow arguments to their logical conclusions. Metaphysical realism assumes that physical reality or has an actual existence independent of a human observer or any act of observation, epistemological realism assumes that progress in science requires strict adherence to scientific mythology, or to the rules and procedures for doing science. If one can accept these assumptions, most of the conclusions drawn should appear fairly self-evident in logical and philosophical terms. And it is also not necessary to attribute any extra-scientific properties to the whole to understand and embrace the new relationship between part and whole and the alternative view of human consciousness that is consistent with this relationship. This is, in this that our distinguishing character between what can be “proven” in scientific terms and what can be reasonably “inferred” in philosophical terms based on the scientific evidence.
Moreover, advances in scientific knowledge rapidly became the basis for the creation of a host of new technologies. Yet, those of which are responsible for evaluating the benefits and risks associated with the use of these technologies, much less their potential impact on human needs and values, normally had expertise on only one side of a two-culture divide. Perhaps, more important, many of the potential threats to the human future - such as, to, environmental pollution, arms development, overpopulation, and spread of infectious diseases, poverty, and starvation - can be effectively solved only by integrating scientific knowledge with knowledge from the social sciences and humanities. We have not done so for a simple reason - the implications of the confusing new fact of nature called non-locality cannot be properly understood without some familiarity wit the actual history of scientific thought. The intent is to suggest that what be most important about this back-ground can be understood in its absence. Those who do not wish to struggle with the small and perhaps, less, then there were fewer in amounts of back-ground implications should feel free to ignore it. But this material will be no more challenging as such, that the hope is that from those of which will find a common ground for understanding and that will meet again on this commonly functions in an effort to close of its circle, resolve the equations of eternity and complete the universe made obtainable to gain into the profound mysteriousness through which its unification holds itself there-within.
Based on what we now know about the evolution of human language abilities, however, it seems clear that our real or actualized self is not imprisoned in our minds. It is implicitly a part of the larger whole of biological life, human observers its existence from embedded relations to this whole, and constructs its reality as based on evolved mechanisms that exist in all human brains. This suggests that any sense of the “otherness” of self and world be is an illusion, in that disguises of its own actualization are to find all its relations between the part that are of their own characterization. Its self as related to the temporality of being whole is that of a biological reality. It can be viewed, of course, that a proper definition of this whole must not include the evolution of the larger undissectible whole. Yet, the cosmos and unbroken evolution of all life, by that of the first self-replication molecule that was the ancestor of DNA. It should include the complex interactions that have proven that among all the parts in biological reality that any resultant of emerging is self-regulating. This, of course, is responsible to properties owing to the whole of what might be to sustain the existence of the parts.
Founded on complications and complex coordinate systems in ordinary language may be conditioned as to establish some developments have been descriptively made by its physical reality and metaphysical concerns. That is, that it is in the history of mathematics and that the exchanges between the mega-narratives and frame tales of religion and science were critical factors in the minds of those who contributed. The first scientific revolution of the seventeenth century, allowed scientists to better them in the understudy of how the classical paradigm in physical reality has marked results in the stark Cartesian division between mind and world that became one of the most characteristic features of Western thought. This is not, however, another strident and ill-mannered diatribe against our misunderstandings, but drawn upon equivalent self realization and undivided wholeness or predicted characterlogic principles of physical reality and the epistemological foundations of physical theory.
Scientific knowledge is an extension of ordinary language into greater levels of abstraction and precision through reliance upon geometry and numerical relationships. We imagine that the seeds of the scientific imagination were planted in ancient Greece. This, of course, opposes any other option but to speculate some displacement afar from the Chinese or Babylonian cultures. Partly because the social, political, and economic climates in Greece were more open in the pursuit of knowledge along with greater margins that reflect upon cultural accessibility. Another important factor was that the special character of Homeric religion allowed the Greeks to invent a conceptual framework that would prove useful in future scientific investigations. But it was only after this inheritance from Greek philosophy was wedded to some essential feature of Judeo-Christian beliefs about the origin of the cosmos that the paradigm for classical physics emerged.
The Greek philosophers we now recognized as the originator’s scientific thoughts were oraclically mystic who probably perceived their world as replete with spiritual agencies and forces. The Greek religious heritage made it possible for these thinkers to attempt to coordinate diverse physical events within a framework of immaterial and unifying ideas. The fundamental assumption that there is a pervasive, underlying substance out of which everything emerges and into which everything returns are attributed to Thales of Miletos. Thales had apparently transcended to this conclusion out of the belief that the world was full of gods, and his unifying substance, water, was similarly charged with spiritual presence. Religion in this instance served the interests of science because it allowed the Greek philosophers to view “essences” underlying and unifying physical reality as if they were “substances.”
The history of science grandly testifies to the manner in which scientific objectivity results in physical theories that must be assimilated into “customary points of view and forms of perception.” The framers of classical physics derived, like the rest of us there, “customary points of view and forms of perception” from macro-level visualized experience. Thus, the descriptive apparatus of visualizable experience became reflected in the classical descriptive categories.
A major discontinuity appears, however, as we moved from descriptive apparatus dominated by the character of our visualizable experience to a complete description of physical reality in relativistic and quantum physics. The actual character of physical reality in modern physics lies largely outside the range of visualizable experience. Einstein, was acutely aware of this discontinuity: “We have forgotten what features of the world of experience caused us to frame pre-scientific concepts, and we have great difficulty in representing the world of experience to ourselves without the spectacles of the old-established conceptual interpretation. There is the further difficulty that our language is compelled to work with words that are inseparably connected with those primitive concepts.”
It is time, for the religious imagination and the religious experience to engage the complementary truths of science in filling that which is silence with meaning. However, this does not mean that those who do not believe in the existence of God or Being should refrain in any sense for assessing the implications of the new truths of science. Understanding these implications does not require to some ontology, and is in no way diminished by the lack of ontology. And one is free to recognize a basis for an exchange between science and religion since one is free to deny that this basis exists - there is nothing in our current scientific world-view that can prove the existence of God or Being and nothing that legitimate any anthropomorphic conceptions of the nature of God or Being. The question of belief in ontology remains what it has always been - a question, and the physical universe on the most basic level remains what has always been - a riddle. And the elemental answer to the question and the ultimate meaning of the riddle is and probably will always be, a matter of personal choice and conviction, in that the finding by some conclusive evidences that openly evince its question, is, much less, that the riddle, is precisely and explicitly relationally found that of, least of mention, a requiring explication that evokes of an immediate introduction for which is the unanswerable representation thereof. In that of its finding as such, their assembling to gather by some inspiring of formidable combinations awaiting the presence to the future. Wherefore, in its secretly enigmatically hidden reservoir lay of the continuous phenomenons, in that, for we are to discover or rediscover upon which the riddle has to undertake by the evincing properties that bind all substantive quantifications raised of all phenomena that adhere to the out-of-the-ordinary endlessnes. That once found might that we realize that its answer belongs but to no man, because once its riddle is solved the owing results are once-more, the afforded efforts gainfully to employ in the obtainable acquirements for which categorize in all of what we seek. In that, the self-naming proclamation belongs only to an overflowing Nothingness, whereby its own bleeding is to call for that which speaks of Nothing. Subsequently, there remains are remnant infractions whose fragments also bleed from their pours as Nothing, for Nothingness means more than Nothingness. If, only to recover in the partialities that unify consciousness, but, once, again, the continuous flow of Nothing gives only to itself the vacuousness that Nothingness belongs of an unchanging endlessness.
Our frame reference point works mostly to incorporate in an abounding classical set affiliation between mind and world, by that lay to some defining features and fundamental preoccupations, for which there is certainly nothing new in the suggestion that contemporary scientific world-view legitimates an alternate conception of the relationship between mind and world. The essential point of attention is that one of “consciousness” and remains in a certain state of our study.
But at the end of this, sometimes labourious journey that precipitate to some conclusion that should make the trip very worthwhile. Initiatory comments offer resistance in contemporaneous physics or biology for believing of the “I” in the stark Cartesian division between mind and world that some have rather aptly described as “the disease of the Western mind.”
Following the fundamental explorations that include questions about knowledge and the intuitive certainty by which but even here the epistemic concepts involved, as this aim is to provide a unified framework for understanding the universe. That in giving the immaterial essences that gave form and structure to this universe were being coded in geometrical and mathematical ideas. And this insight led him to invented algebraic geometry.
A scientific understanding to these ideas could be derived, as did that Descartes declared, that with the aid of precise deduction, and he also claimed that the contours of physical reality could be laid out in three-dimensional coordinates. In classical physics, external reality consisted of inert and inanimate matter moving according to wholly deterministic natural laws, and collections of discrete atomized parts made up wholes. Classical physics was also premised, however, a dualistic conception of reality as consisting of abstract disembodied ideas existing in a domain separate form and superior to sensible objects and movements. The notion that the material world experienced by the senses was inferior to the immaterial world experienced by mind or spirit has been blamed for frustrating the progress of physics up too at least the time of Galileo. But in one very important respect, it also made the first scientific revolution possible. Copernicus, Galileo, Kepler, and Newton firmly believed that the immaterial geometrical and mathematical ideas that inform physical reality had a prior existence in the mind of God and that doing physics was a form of communion with these ideas.
The tragedy of the Western mind is a direct consequence of the stark Cartesian division between mind and world. This is the tragedy of the modern mind which “solved the riddle of the universe,” but only to replace it by another riddle: The riddle of itself. Yet, we discover the “certain principles of physical reality,” said Descartes, “not by the prejudices of the senses, but by rational analysis, which thus possess so great evidence that we cannot doubt of their truth.” Since the real, or that which actually remains external to ourselves, was in his view only that which could be represented in the quantitative terms of mathematics, Descartes concluded that all qualitative aspects of reality could be traced to the deceitfulness of the senses.
Given that Descartes distrusted the information from the senses to the point of doubting the perceived results of repeatable scientific experiments, how did he conclude that our knowledge of the mathematical ideas residing only in mind or in human subjectivity was accurate, much less the absolute truth? He did so by making a leap of faith - God constructed the world, said Descartes, according to the mathematical ideas that our minds could uncover in their pristine essence. The truths of classical physics as Descartes viewed them were quite literally “revealed” truths, and it was this seventeenth-century metaphysical presupposition that became in the history of science what is termed the “hidden ontology of classical epistemology.” Descartes lingers in the widespread conviction that science does not provide a “place for man” or for all that we know as distinctly human in subjective reality.
The historical notion in the unity of consciousness has had an interesting history in philosophy and psychology. Taking Descartes to be the first major philosopher of the modern period, the unity of consciousness was central to the study of the mind for the whole of the modern period until the 20th century. The notion figured centrally in the work of Descartes, Leibniz, Hume, Reid, Kant, Brennan, James, and, in most of the major precursors of contemporary philosophy of mind and cognitive psychology. It played a particularly important role in Kant's work.
A couple of examples will illustrate the role that the notion of the unity of consciousness played in this long literature. Consider a classical argument for dualism (the view that the mind is not the body, indeed is not made out of matter at all). It starts like this: When I consider the mind, which is to say of myself, as far as I am only a thinking thing, I cannot distinguish in myself any parts, but apprehend myself to be clearly one and entire.
Here is another, more elaborate argument based on unified consciousness. The conclusion will be that any system of components could never achieve unified consciousness acting in concert. William James' well-known version of the argument starts as follows: Take a sentence of a dozen words, take twelve men, and to each word. Then stand the men in a row or jam them in a bunch, and let each think of his word as intently as he will; Nowhere will there be a consciousness of the whole sentence.
James generalizes this observation to all conscious states. To get dualism out of this, we need to add a premise: That if the mind were made out of matter, conscious states would have to be distributed over some group of components in some relevant way. Nevertheless, this thought experiment is meant to show that conscious states cannot be so distributed. Therefore, the conscious mind is not made out of matter. Calling the argument that James is using is the Unity Argument. Clearly, the idea that our consciousness of, here, the parts of a sentence are unified is at the centre of the Unity Argument. Like the first, this argument goes all the way back to Descartes. Versions of it can be found in thinkers otherwise as different from one another as Leibniz, Reid, and James. The Unity Argument continued to be influential into the 20th century. That the argument was considered a powerful reason for concluding that the mind is not the body is illustrated in a backhanded way by Kant's treatment of it (as he found it in Descartes and Leibniz, not James, of course).
Kant did not think that we could uncover anything about the nature of the mind, including whether nor is it made out of matter. To make the case for this view, he had to show that all existing arguments that the mind is not material do not work and he set out to do justly that in the Critique of Pure Reason on the Paralogisms of Pure Reason (1781) (paralogisms are faulty inferences about the nature of the mind). The Unity Argument is the target of a major part of that chapter; if one is going to show that we cannot know what the mind is like, we must dispose of the Unity Argument, which purports to show that the mind is not made out of matter. Kant's argument that the Unity Argument does not support dualism is simple. He urges that the idea of unified consciousness being achieved by something that has no parts or components are no less mysterious than its being achieved by a system of components acting together. Remarkably enough, though no philosopher has ever met this challenge of Kant's and no account exists of what an immaterial mind not made out of parts might be like, philosophers continued to rely on the Unity Argument until well into the 20th century. It may be a bit difficult for us to capture this now but the idea any system of components, and for an even stronger reason might not realize that merge with consciousness, that each system of material components, had a strong intuitive appeal for a long time.
The notion that consciousness agrees to unification and was in addition central to one of Kant's own famous arguments, his ‘transcendental deduction of the categories’. In this argument, boiled down to its essentials, Kant claims that to tie various objects of experience together into a single unified conscious representation of the world, something that he simply assumed that we could do, we could probably apply certain concepts to the items in question. In particular we have to apply concepts from each of four fundamental categories of concept: Quantitative, qualitative, relational, and what he called ‘modal’ concepts. Modal concept’s concern of whether an item might exist, does exist, or must exist. Thus, the four kinds of concept are concepts for how many units, what features, what relations to other objects, and what existence status is represented in an experience.
It was relational conceptual representation that most interested Kant and of relational concepts, he thought the concept of cause-and-effect to be by far the most important. Kant wanted to show that natural science (which for him meant primarily physics) was genuine knowledge (he thought that Hume's sceptical treatment of cause and effect relations challenged this status). He believed that if he could prove that we must tie items in our experience together causally if we are to have a unified awareness of them, he would have put physics back on "the secure path of a science.” The details of his argument have exercised philosophers for more than two hundred years. We will not go into them here, but the argument illustrates how central the notion of the unity of consciousness was in Kant's thinking about the mind and its relation to the world.
Although the unity of consciousness had been at the centre of pre-20th century research on the mind, early in the 20th century the notion almost disappeared. Logical atomism in philosophy and behaviourism in psychology were both unsympathetic to the notion. Logical atomism focussed on the atomic elements of cognition (sense data, simple propositional judgments, etc.), rather than on how these elements are tied together to form a mind. Behaviourism urged that we focus on behaviour, the mind being alternatively myth or something otherwise that we cannot and do not need of studying the mysteriousness of science, from which brings meaning and purpose to humanity. This attitude extended to consciousness, of course. The philosopher Daniel Dennett summarizes the attitude prevalent at the time this way: Consciousness may be the last bastion of occult properties, epiphenomena, immeasurable subjective states - in short, the one area of mind best left to the philosophers. Let them make fools of themselves trying to corral the quicksilver of ‘phenomenology’ into a respectable theory.
The unity of consciousness next became an object of serious attention in analytic philosophy only as late as the 1960s. In the years since, new work has appeared regularly. The accumulated literature is still not massive but the unity of consciousness has again become an object of serious study. Before we examine the more recent work, we need to explicate the notion in more detail than we have done so far and introduce some empirical findings. Both are required to understand recent work on the issue.
To expand on our earlier notion of the unity of consciousness, we need to introduce a pair of distinctions. Current works on consciousness labours under a huge, confusing terminology. Different theorists exchange dialogue over the excess consciousness, phenomenal consciousness, self-consciousness, simple consciousness, creature consciousness, states consciousness, monitoring consciousness, awareness as equated with consciousness, awareness distinguished from consciousness, higher orders thought, higher orders experience, Qualia, the felt qualities of representations, consciousness as displaced perception, . . . and on and on and on. We can ignore most of this profusion but we do need two distinctions: between consciousness of objects and consciousness of our representations of objects, and between consciousness of representations and consciousness of self.
It is very natural to think of self-consciousness or, cognitive state more accurately, as a set of cognitive states. Self-knowledge is an example of such a cognitive state. There are plenty of things that I know bout self. I know the sort of thing I am: a human being, a warm-blooded rational animal with two legs. I know of many properties and much of what is happening to me, at both physical and mental levels. I also know things about my past, things I have done and that of whom I have been with other people I have met. But I have many self-conscious cognitive states that are not instances of knowledge. For example, I have the capacity to plan for the future - to weigh up possible courses of action in the light of goals, desires, and ambitions. I am capable of ca certain type of moral reflection, tide to moral self-and understanding and moral self-evaluation. I can pursue questions like, what sort of person I am? Am I the sort of person I want to be? Am I the sort of individual that I ought to be? This is my ability to think about myself. Of course, much of what I think when I think about myself in these self-conscious ways is also available to me to employing in my thought about other people and other objects.
When I say that I am a self-conscious creature, I am saying that I can do all these things. But what do they have in common? Could I lack some and still be self-conscious? These are central questions that take us to the heart of many issues in metaphysics, the philosophy of mind, and the philosophy of psychology.
And, if, in at all, a straightforward explanation to what makes those of the “self contents” immune to error through misidentification concerning the semantics of self, then it seems fair to say that the problem of self-consciousness has been dissolved, at least as much as solved.
This proposed account would be on a par with other noted examples as such as the redundancy theory of truth. That is to say, the redundancy theory or the deflationary view of truth claims that the predicate ‘ . . . true’ does not have a sense, i.e., expresses no substantive or profound or explanatory concept that ought to be the topic of philosophic enquiry. The approach admits of different versions, but centres on the pints (1) that ‘it is true that p’ says no more nor less than ‘p’ (so, redundancy”) (2) that in less direct context, such as ‘everything he said was true’, or ‘all logical consequences of true propositions as true’, the predicated functions as a device enabling us to generalize rather than as an adjective or predicate describing the things he said, or the kinds of propositions that follow from true propositions. For example, its translation is to infer that: (œ p, Q)(P & p
q
q)’ where there is no use of a notion of truth.
There are technical problems in interpreting all uses of the notion of truth in such ways, but they are not generally felt to be insurmountable. The approach needs to explain away apparently substantive uses of the notion, such as . . . ‘science aims at the truth’ or ‘truth is a norm governing discourse. Indeed, postmodernist writing frequently advocates that we must abandon such norms, along with a discredited ‘objective’ concept ion of truth. But perhaps, we can have the norms even when objectivity is problematic, since they can be framed within mention of truth: Science wants to be so that whenever science holds that ‘p’, when ‘p’‘. Discourse is to be regulated by the principle that it is wrong to assert ‘p’. When not-p.
Confronted with the range of putatively self-conscious cognitive states, one might assume that there is a single ability that is presupposed. This is my ability to think about myself, and I can only have knowledge about myself if I have beliefs about myself, and I can only have beliefs about myself if I can entertain thoughts about myself. The same can be said for auto-graphical memories and moral self-understanding. These are ways of thinking about myself.
Of course, much of what I think when I think about myself in these self-conscious ways is also available to me to employ in my thoughts about other people and other objects. My knowledge that I am a human being deploys certain conceptual abilities that I can also deploy in thinking that you are a human being. The same holds when I congratulate myself for satisfying the exacting moral standards of autonomous moral agencies. This involves concepts and descriptions that can apply equally to me and to others. On the other hand, when I think about myself, I am also putting to work an ability that I cannot put to work in thinking about other people and other objects. This is precisely the ability to apply those concepts and descriptions to myself. It has become common to refer to this ability as the ability to entertain “I’-thoughts.
What is an, “I”-thought?” Obviously, an “I”-thought is a thought that involves self-reference. I can think an “I”-thought only by thinking about myself. Equally obvious, though, this cannot be all that there is to say on the subject. I can think thoughts that involve a self-reference but am not “I”-thoughts. Suppose I think that the next person to set a parking ticket in the centre of Toronto deserves everything he gets. Unbeknown to be, the very next recipient of a parking ticket will be me. This makes my thought self-referencing, but it does not make it an “I”-thought. Why not? The answer is simply that I do not know that I will be the next person to get a parking ticket in the down-town area in Toronto. Is ‘A’, is that unfortunate person, then there is a true identity statement of the form I = A, but I do not know that this identity holds, I cannot be ascribed the thoughts that I will deserve everything I get? And say I am not thinking genuine “I”-thoughts, because one cannot think a genuine “I”-thought if one is ignorant that one is thinking about one’s self. So it is natural to conclude that “I”-thoughts involve a distinctive type of self-reference. This is the sort of self-reference whose natural linguistic expression is the first-person pronoun “I,” because one cannot be the first-person pronoun without knowing that one is thinking about oneself.
This is still not quite right, however, because thought contents can be specific, perhaps, they can be specified directly or indirectly. That is, all cognitive states to be considered, presuppose the ability to think about oneself. This is not only that they all have to some commonality, but it is also what underlies them all. We can see is more detail what this suggestion amounts to. This claim is that what makes all those cognitive states modes of self-consciousness is the fact that they all have content that can be specified directly by means of the first person pronoun “I” or, indirectly by means of the direct reflexive pronoun “he,” such they are first-person contents.
The class of first-person contents is not a homogenous class. There is an important distinction to be drawn between two different types of first-person contents, corresponding to two different modes in which the first person can be employed. The existence of this distinction was first noted by Wittgenstein in an important passage from The Blue Book: That there are two different cases in the use of the word “I” (or, “my”) which is called “the use as object” and “the use as subject.” Examples of the first kind of use are these” “My arm is broken,” “I have grown six inches,” “I have a bump on my forehead,” “The wind blows my hair about.” Examples of the second kind are: “I see so-and-so,” “I try to lift my arm,” “I think it will rain,” “I have a toothache.”
The explanations given are of the distinction that hinge on whether or not they are judgements that involve identification. However, one can point to the difference between these two categories by saying: The cases of the first category involve the recognition of a particular person, and there is in these cases the possibility of an error, or as: The possibility of can error has been provided for . . . It is possible that, say in an accident, I should feel a pain in my arm, see a broken arm at my side, and think it is mine when really it is my neighbour’s. And I could, looking into a mirror, mistake a bump on his forehead for one on mine. On the other hand, there is no question of recognizing a person when I say I have toothache. To ask “are you sure that its you who have pains?” Its one and only, would be nonsensical.
Wittgenstein is drawing a distinction between two types of first-person contents. The first type, which is describes as invoking the use of “I” as object, can be analysed in terms of more basic propositions. Such that the thought “I am B” involves such a use of “I.” Then we can understand it as a conjunction of the following two thoughts” “a is B” and “I am a.” We can term the former a predication component and the latter an identification component. The reason for braking the original thought down into these two components is precisely the possibility of error that Wittgenstein stresses in the second passages stated. One can be quite correct in predicating that someone is ‘B’, even though mistaken in identifying oneself as that person.
To say that a statement “a is B” is subject to error through misidentification relative to the term “a” means that the following is possible: The speaker knows some particular thing to be “B,” but makes the mistake of asserting “a is B” because, and only because, he mistakenly thinks that the thing he knows to be “B” is what “a” refers to.
The give direction to, then, is that one cannot be mistaken about who is being thought about. In one sense, Shoemaker’s criterion of immunity to error through misidentification relative to the first-person pronoun (simply “immunity to error through misidentification”) is too restrictive. Beliefs with first-person contents that are immune to error through identification tend to be acquired on grounds that usually do result in knowledge, but they do not have to be. The definition of immunity to error trough misidentification needs to be adjusted to accommodate them by formulating it in terms of justification rather than knowledge.
The connection to be captured is between the sources and grounds from which a belief is derived and the justification there is for that belief. Beliefs and judgements are immune to error through misidentification in virtue of the grounds on which they are based. The category of first-person contents being picked out is not defined by its subject matter or by any points of grammar. What demarcates the class of judgements and beliefs that are immune to error through misidentification is evidence base from which they are derived, or the information on which they are based. So, to take by example, my thought that I have a toothache is immune to error through misidentification because it is based on my feeling a pain in my teeth. Similarly, the fact that I am consciously perceiving you makes my belief that I am seeing you immune to error through misidentification.
To say that a statement “a is B” is subject to error through misidentification relative to the term “a” means that some particular thing is B, because his belief is based on an appropriate evidence base, but he makes the mistake of asserting “a is B” because, and only because, he mistakenly thinks that the thing he justified believes to be ‘B’ is what “a” refers to.
Beliefs with first-person contents that are immune to error through misidentification tend to be acquired on grounds that usually result in knowledge, but they do not have to be. The definition of immunity to error through misidentification needs to be adjusted to accommodate by formulating in terms of justification than knowledge. The connection to be captured is between the sources and grounds from which a belief is derived and the justification there is for that belief. Beliefs and judgements are immune to error through misidentification in virtue of the grounds on which they are based. The category of first-person contents picked out is not defined by its subject matter or by any points of grammar. What demarcates the class of judgements and beliefs that ae immune to error through misidentification is the evidence base from which they are derived, or the information on which they are based. For example, my thought that I have a toothache is immune to error through misidentification because it is based on my feeling a pain in my teeth. Similarly, the fact that I am consciously perceiving you makes my belief that I am seeing you immune to error through misidentification.
A suggestive definition is to enounce that a statement “a is b” is subject to error through misidentification relative to the term “a” means that the following is possible: The speaker is warranted in believing that some particular thing is “b,” because his belief is based on an appropriate evidence base, but he makes the mistake of asserting “a is b” because, and only because, he mistakenly thinks that the thing he justified believes to be “b” is what “a” refers to.
First-person contents that are immune to error through misidentification can be mistaken, but they do have a basic warrant in virtue of the evidence on which they are based, because the fact that they are derived from such an evidence base is closely linked to the fact that they are immune to error thought misidentification. Of course, there is room for considerable debate about what types of evidence base ae correlated with this class of first-person contents. Seemingly, then, that the distinction between different types of first-person content can be characterized in two different ways. We can distinguish between those first-person contents that are immune to error through misidentification and those that are subject to such error. Alternatively, we can discriminate between first-person contents with an identification component and those without such a component. For purposes rendered, in that these different formulations each pick out the same classes of first-person contents, although in interestingly different ways.
All first-person consent subject to error through misidentification contains an identification component of the form “I am a” and employ of the first-person-pronoun contents with an identification component and those without such a component. in that identification component, does it or does it not have an identification component? Acquitted by the pain of some infinite regress, at some stage we will have to arrive at an employment of the first-person pronoun that does not have to arrive at an employment of the first-person pronoun that does not presuppose an identification component, then, is that any first-person content subject to error through misidentification will ultimately be anchored in a first-person content that is immune to error through misidentification.
It is also important to stress how self-consciousness, and any theory of self-consciousness that accords a serious role in self-consciousness to mastery of the semantics of the first-person pronoun, are motivated by an important principle that has governed much if the development of analytical philosophy. This is the principle that the philosophical analysis of though can only proceed through the principle analysis of language. The principle has been defended most vigorously by Michael Dummett.
Even so, thoughts differ from that is said to be among the contents of the mind in being wholly communicable: It is of the essence of thought that I can convey to you the very thought that I have, as opposed to being able to tell you merely something about what my though is like. It is of the essence of thought not merely to be communicable, but to be communicable, without residue, by means of language. In order to understand thought, it is necessary, therefore, to understand the means by which thought is expressed. Dummett goes on to draw the clear methodological implications of this view of the nature of thought: We communicate thoughts by means of language because we have an implicit understanding of the workings of language, that is, of the principles governing the use of language, it is these principles, which relate to what is open to view in the mind other than via the medium of language that endow our sentences with the senses that they carry. In order to analyse thought, therefore, it is necessary to make explicit those principles, regulating our use of language, which we already implicitly grasp.
Many philosophers would want to dissent from the strong claim that the philosophical analysis of thought through the philosophical analysis of language is the fundamental task of philosophy. But there is a weaker principle that is very widely held as The Thought-Language Principle.
As it stands, the problem between to different roles that the pronoun “he” can play of such oracle clauses. On the one hand, “he” can be employed in a proposition that the antecedent of the pronoun (i.e., the person named just before the clause in question) would have expressed using the first-person pronoun. In such a situation that holds that “he,” is functioning as a quasi-indicator. Then when “he” is functioning as a quasi-indicator, it is written as “he.” Others have described this as the indirect reflexive pronoun. When “he” is functioning as an ordinary indicator, it picks out an individual in such a way that the person named just before the clause of opacity need not realize the identity of himself with that person. Clearly, the class of first-person contents is not homogenous class.
A subject has distinguished self-awareness to the extent that he is able to distinguish himself from the environment and its content. He has been distinguishing psychological self-awareness to the extent that he is able to distinguish himself as a psychological subject within a contract space of other psychological subjects. What does this require? The notion of a non-conceptual point of view brings together the capacity to register one’s distinctness from the physical environment and various navigational capacities that manifest a degree of understanding of the spatial nature of the physical environment. One very basic reason for thinking that these two elements must be considered together emerges from a point made in the richness of the self-awareness that accompanies the capacity to distinguish the self from the environment is directly proportion are to the richness of the awareness of the environment from which the self is being distinguished. So no creature can understand its own distinction from the physical enjoinment without having an independent understanding of the nature of the physical environment, and since the physical environment is essentially spatial, this requires an understanding of the spatial nature of the physical environment. but this cannot be the whole story. It leaves unexplained why an understanding should be required of this particular essential feature of the physical environment. After all, it is also an essential feature of the physical environment that it is composed of an object that has both primary and secondary qualities, but there is a reflection of this in the notion of a non-conceptual point of view. More is needed to understand the significance of spatiality.
The very idea of a perceived objective spatial world brings with it the ideas of the subject for being in the world, which there course of his perceptions due to his changing position in the world and to the more or less stable in the way of the world is. The idea that there is an objective world and the idea that the subject is somewhere cannot be separated, and where he is given by what he can perceive.
But the main criteria of his work is ver much that the dependence holds equally in the opposite direction.
It seems that this general idea can be extrapolated and brought to bar on the notion of a non-conceptual point of view. What binds together the two apparently discrete components of a non-conceptual point of view is precisely the fact that a creature’s self-awareness must be awareness of itself as a spatial bing that acts upon and is acted upon by the spatial world. Evans’s own gloss on how a subject’s self-awareness, is awareness of himself as a spatial being involves the subject’s mastery of a simple theory explaining how the world makes his perceptions as they are, with principles like “I perceive such and such, such and such holds at ‘P’; so (probably) am ‘P’ and “I’’: am ‘P?’, such does not hold at ‘P’, so I cannot really be perceiving such and such, even though it appears that I am” (Evans 1982). This is not very satisfactory, though. If the claim is that the subject must explicitly hold these principles, then it is clearly false. If, on the other hand, the claim is that these are the principles of a theory that a self-conscious subject must tacitly know, then the claim seems very uninformative in the absence of any specification of the precise forms of behaviour that can only be explained by there ascription to a body of tacit knowledge. We need an account of what it is for a subject to be correctly described as possessing such a simple theory of perception. The point however, is simply that the notion of as non-conceptual point of view as presented, can be viewed as capturing, at a more primitive level, precisely the same phenomenon that Evans is trying to capture with his notion of a simple theory of perception.
Moreover, stressing the importance of action and movement indicates how the notion of a non-conceptual point of view might be grounded in the self-specifying in for action to be found in visual perception. By that in thinking particularly of the concept of an affordance so central to Gibsonian theories of perception. One important type of self-specifying information in the visual field is information about the possibilities for action and reaction that the environment affords the perceiver, by which that affordancs are non-conceptual first-person contents. The development of a non-conceptual point of view clearly involves certain forms of reasoning, and clearly, we will not have a full understanding of he the notion of a non-conceptual point of view until we have an explanation of how this reasoning can take place. The spatial reasoning engaged over which this reasoning takes place. The spatial reasoning involved in developing a non-conceptual point of view upon the world is largely a matter of calibrating different affordances into an integrated representation of the world.
In short, any learned cognitive ability is contractible out of more primitive abilities already in existence. There are good reasons to think that the perception of affordance is innate. And so if, the perception of affordances is the key to the acquisition of an integrated spatial representation of the environment via the recognition of affordance symmetries, affordance transitivities, and affordance identities, then it is precisely conceivable that the capacities implicated in an integrated representation of the world could emerge non-mysteriously from innate abilities.
Nonetheless, there are many philosophers who would be prepared to countenance the possibility of non-conceptual content without accepting that to use the theory of non-conceptual content so solve the paradox of self-consciousness. This is ca more substantial task, as the methodology that is adapted rested on the first of the marks of content, namely that content-bearing states serve to explain behaviour in situations where the connections between sensory input and behaviour output cannot be plotted in a law-like manner (the functionalist theory of self-reference). As such, not of allowing that every instance of intentional behaviour where there are no such law-like connections between sensory input and behaviour output needs to be explained by attributing to the creature in question of representational states with first-person contents. Even so, many such instances of intentional behaviour do need to be explained in this way. This offers a way of establishing the legitimacy of non-conceptual first-person contents. What would satisfactorily demonstrate the legitimacy of non-conceptual first-person contents would be the existence of forms of behaviour in paralinguistic or nonlinguistic creatures for which inference to the best understanding or explanation (which in this context includes inference to the most parsimonious understanding, or explanation) demands the ascription of states with non-conceptual first-person contents.
The non-conceptual first-person contents and the pick-up of self-specifying information in the structure of exteroceptive perception provide very primitive forms of non-conceptual self-consciousness, even if forms that can plausibly be viewed as in place of one’s birth or shortly afterward. The dimension along which forms of self-consciousness must be compared is the richest of the conception of the self that they provide. All of which, a crucial element in any form of self-consciousness is how it enables the self-conscious subject to distinguish between self and environment - what many developmental psychologists term self-world dualism. In this sense, self-consciousness is essentially a contrastive notion. One implication of this is that a proper understanding of the richness of the conception that we take into account the richness of the conception of the environment with which it is associated. In the case of both somatic proprioception and the pick-up of self-specifying information in exteroceptive perception, there is a relatively impoverished conception of the environment. One prominent limitation is that both are synchronic than diachronic. The distinction between self and environment that they offer is a distinction that is effective at a time but not over time. The contrast between propriospecific and exterospecific invariant in visual perception, for example, provides a way for a creature to distinguish between itself and the world at any given moment, but this is not the same as a conception of oneself as an enduring thing distinguishable over time from an environment that also endures over time.
The notion of a non-conceptual point of view brings together the capacity to register one’s distinctness from the physical environment and various navigational capacities that manifest a degree of understanding of the spatial nature of the physical environment. One very basic reason for thinking that these elements must be considered together emerges from a point made from which the richness of the awareness of the environment from which the self is being distinguished. So no creature can understand its own distinctness from the physical environment without having an independent understanding of the nature of the physical environment, and since the physical environment is essentially spatial, this requires an understanding of the spatial nature of the physical environment. But this cannot be the whole story. It leaves unexplained why an understanding should be required of this particular essential feature of the physical environment. After all, it is also an essential feature of the physical environment that it is composed of objects that have both primary and secondary qualities, but there is no reflection of this in the notion of a non-conceptual point of view. More is needed to understand the significance of spatiality.
The general idea is very powerful, that the relevance of spatiality to self-consciousness comes about not merely because the world is spatial but also because the self-conscious subject is himself a spatial element of the world. One cannot be self-conscious without being aware that one is a spatial element of the world, and one cannot be aware that one is a spatial element of the world, and one cannot be aware that one is a spatial element of the world without a grasp of the spatial nature of the world.
The very idea of perceivable, objective spatial wold bings it the idea of the subject for being in the world, with the course of his perceptions due to his changing position in the world and to the more or less stable way the world is. The idea that there is an objective world and the idea that the subject is somewhere cannot be separated, and where he is given by what he can perceive.
One possible reaction to consciousness, is that it is erroneously only because unrealistic and ultimately unwarranted requirements are being placed on what is to count as genuinely self-referring first-person thoughts. Suppose for such an objection will be found in those theories that attempt to explain first-person thoughts in a way that does not presuppose any form of internal representation of the self or any form of self-knowledge. Consciousness arises because mastery of the semantics of the first-person pronoun is available only to creatures capable of thinking first-person thoughts whose contents involve reflexive self-reference and thus, seem to presuppose mastery of the first-person pronoun. If, thought, it can be established that the capacity to think genuinely first-person thoughts does not depend on any linguistic and conceptual abilities, then arguably the problem of circularity will no longer have purchase.
There is no account of self-reference and genuinely first-person thought that can be read in a way that poses just such a direct challenge to the account of self-reference underpinning the conscious. This is the functionalist account, although spoken before, the functionalist view, reflexive self-reference is a completely unmysterious phenomenon susceptible to a functional analysis. Reflexive self-reference is not dependent upon any antecedent conceptual or linguistic skills. Nonetheless, the functionalist account of a reflexive self-reference is deemed to be sufficiently rich to provide the foundation for an account of the semantics of the first-person pronoun. If this is right, then the circularity at which consciousness is at its heart, and can be avoided.
The circularity problems at the root of consciousness arise because mastery of the semantics of the first-person pronoun requires the capacity to think fist-person thoughts whose natural expression is by means of the first-person pronoun. It seems clear that the circle will be broken if there are forms of first-person thought that are more primitive than those that do not require linguistic mastery of the first-person pronoun. What creates the problem of capacity circularity is the thought that we need to appeal to first-person contents in explaining mastery of the first-person pronoun, whereby its containing association with the thought that any creature capable of entertaining first-person contents will have mastered the first-person pronoun. So if we want to retain the thought that mastery of the first-person pronoun can only be explained in terms of first-person contents, capacity circularity can only be avoided if there are first-person contents that do not presuppose mastery of the first-person pronoun.
On the other hand, however, it seems to follow from everything earlier mentioned about “I”-thoughts that conscious thought in the absence of linguistic mastery of the first-person pronoun is a contradiction in terms. First-person thoughts have first-person contents, where first-person contents can only be specified in terms of either the first-person pronoun or the indirect reflexive pronoun. So how could such thoughts be entertained by a thinker incapable of a reflexive self-reference? How can a thinker who is not capable of reflexively reference? How can a thinker who is not the first-person pronoun be plausibly ascribed thoughts with first-person contents? The thought that, despite all this, there are real first-person contents that do not presuppose mastery of the first-person pronoun is at the core of the functionalist theory of self-reference and first-person belief.
The best developed functionalist theory of self-reference has been provided by Hugh Mellor (1988-1089). The basic phenomenon he is interested in explaining is what it is for a creature to have what he terms a “subjective belief,” that is to say, a belief whose content is naturally expressed by a sentence in the first-person singular and the present tense. The explanation of subjective belief that he offers makes such beliefs independent of both linguistic abilities and conscious beliefs. From this basic account he constructs an account of conscious subjective beliefs and the of the reference of the first-person pronoun “I.” These putatively more sophisticated cognitive states are casually derivable from basic subjective beliefs.
Historically, Heidegger' theory of spatiality distinguishes three different types of space: (1) world-space, (2) regions (Gegend), and (3) Dasein's spatiality. What Heidegger calls "world-space" is space conceived as an “arena” or “container” for objects. It captures both our ordinary conception of space and theoretical space - in particular absolute space. Chairs, desks, and buildings exist “in” space, but world-space is independent of such objects, much like absolute space “in which” things exist. However, Heidegger thinks that such a conception of space is an abstraction from the spatial conduct of our everyday activities. The things that we deal with are near or far relative to us; according to Heidegger, this nearness or farness of things is how we first become familiar with that which we (later) represented to ourselves as "space." This familiarity with which are rendered the understanding of space (in a "container" metaphor or in any other way) possible. It is because we act spatially, going to places and reaching for things to use, that we can even develop a conception of abstract space at all. What we normally think of as space - world-space - turns out not to be what space fundamentally is; world-space is, in Heidegger's terminology, space conceived as vorhanden. It is an objectified space founded on a more basic space-of-action.
Since Heidegger thinks that space-of-action is the condition for world-space, he must explain the former without appealing to the latter. Heidegger's task then is to describe the space-of-action without presupposing such world-space and the derived concept of a system of spatial coordinates. However, this is difficult because all our usual linguistic expressions for describing spatial relations presuppose world-space. For example, how can one talk about the "distance between you and me" without presupposing some sort of metric, i.e., without presupposing an objective access to the relation? Our spatial notions such as "distance," "location," etc. must now be re-described from a standpoint within the spatial relation of self (Dasein) to the things dealt with. This problem is what motivates Heidegger to invent his own terminology and makes his discussion of space awkward. In what follows I will try to use ordinary language whenever possible to explain his principal ideas.
The space-of-action has two aspects: regions (space as Zuhandenheit) and Dasein's spatiality (space as Existentiale). The sort of space we deal within our daily activity is "functional" or zuhanden, and Heidegger's term for it is "region." The places we work and live-the office, the park, the kitchen, etc.-all having different regions that organizes our activities and conceptualized “equipment.” My desk area as my work region has a computer, printer, telephone, books, etc., in their appropriate “places,” according to the spatiality of the way in which I work. Regions differ from space viewed as a "container"; the latter notion lacks a "referential" organization with respect to our context of activities. Heidegger wants to claim that referential functionality is an inherent feature of space itself, and not just a "human" characteristic added to a container-like space.
In our activity, how do we specifically stand with respect to functional space? We are not "in" space as things are, but we do exist in some spatially salient manner. What Heidegger is trying to capture is the difference between the nominal expression "we exist in space" and the adverbial expression "we exist spatially." He wants to describe spatiality as a mode of our existence rather than conceiving space as an independent entity. Heidegger identifies two features of Dasein's spatiality - "de-severance" (Ent-fernung) and "directionality" (Ausrichtung).
De-severance describes the way we exist as a process of spatial self-determination by “making things available” to ourselves. In Heidegger's language, in making things available we "take in space" by "making the farness vanish" and by "bringing things close"
We are not simply contemplative beings, but we exist through concretely acting in the world - by reaching for things and going to places. When I walk from my desk area into the kitchen, I am not simply alternating locations from points ‘A’ to ‘B’ in an arena-like space, but I am “taking in space” as I move, continuously making the “farness” of the kitchen “vanish,” as the shifting spatial perspectives are opened as I go along.
This process is also inherently "directional." Every de-severing is aimed toward something or in a certain direction that is determined by our concern and by specific regions. I must always face and move in a certain direction that is dictated by a specific region. If I want to get a glass of ice tea, instead of going out into the yard, I face toward the kitchen and move in that direction, following the region of the hallway and the kitchen. Regions determine where things belong, and our actions are coordinated in directional ways accordingly.
De-severance, directionality, and regionality are three ways of describing the spatiality of a unified Being-in-the-world. As aspects of Being-in-the-world, these spatial modes of being are equiprimordial.9 10 Regions "refer" to our activities, since they are established by our ways of being and our activities. Our activities, in turn, are defined in terms of regions. Only through the region can our de-severance and directionality are established. Our object of concern always appears in a certain context and place, in a certain direction. It is because things appear in a certain direction and in their places “there” that we have our “here.” We orient ourselves and organize our activities, always within regions that must already be given to us.
Heidegger's analysis of space does not refer to temporal aspects of Being-in-the-world, even though they are presupposed. In the second half of Being and Time he explicitly turns to the analysis of time and temporality in a discussion that is significantly more complex than the earlier account of spatiality. Heidegger makes the following five distinctions between types of time and temporality: (1) The ordinary or "vulgar" conception of time; this is time conceived as Vorhandenheit. (2) World-time; this is time as Zuhandenheit. Dasein's temporality is divided into three types: (3) Dasein's inauthentic (uneigentlich) temporality, (4) Dasein's authentic (eigentlich) temporality, and (5) originary temporality or “temporality as such.” The analyses of the vorhanden and zuhanden modes of time are interesting, but it is Dasein's temporality that is relevant to our discussion, since it is this form of time that is said to be founding for space. Unfortunately, Heidegger is not clear about which temporality plays this founding role.
We can begin by excluding Dasein's inauthentic temporality. This mode of time refers to our unengaged, "average" way in which we regard time. It is the “past we forget” and the “future we expect,” all without decisiveness and resolute understanding. Heidegger seems to consider that this mode of a temporality is the temporal dimension of de-severance and directionality, since de-severance and directionality deal only with everyday actions. As such, is the inauthenticity founded within a temporality that must in themselves be set up in an authentic basis of some sort. The two remaining candidates for the foundation are Dasein's authentic temporality and originary temporality.
Dasein's authentic temporality is the "resolute" mode of temporal existence. An authentic temporality is realized when Dasein becomes aware of its own finite existence. This temporality has to do with one's grasp of his or her own life as a whole from one's own unique perspective. Life gains meaning as one's own life-project, bounded by the sense of one's realization that he or she is not immortal. This mode of time appears to have a normative function within Heidegger's theory. In the second half of BT he often refers to inauthentic or "everyday" mode of time as lacking some primordial quality which authentic temporality possesses.
In contrast, an originary temporality is the formal structure of Dasein's temporality itself. In addition to its spatial Being-in-the-world, Dasein also exists essentially as "projection." Projection is oriented toward the future, and this coming orientation regulates our concern by constantly realizing various possibilities. A temporality is characterized formally as this dynamic structure of "a future that makes present in the process of having been." Heidegger calls the three moments of temporality - the future, the present, and the past - the three ecstasies of the temporality. This mode of time is not normative but rather formal or neutral; as Blattner argues, the temporal features that constitute Dasein's temporality describe both inauthentic and authentic temporalities.
There are some passages that indicate that authentic temporality is the primary manifestation of the temporality, because of its essential orientation toward the future. For instance, Heidegger states that "temporality first showed itself in anticipatory resoluteness." Elsewhere, he argues that "the ‘time’ which is accessible to Dasein's common sense is not primordial, but arises rather from authentic temporality." In these formulations, authentic to the temporality is said to find of other inauthentic modes. According to Blattner, this is "by far the most common" interpretation of the status of authentic time.
However, to argue with Blattner and Haar, in that there are far more passages where Heidegger considers an originary temporality as distinct from authentic temporality, and founding for it and for Being-in-the-world as well. Here are some examples: The temporality has different possibilities and different ways of temporalizing itself. The basic possibilities of existence, the authenticity and inauthenticity of Dasein, are grounded ontologically on possible temporalizations of temporality. Time is primordial as the temporalizing of a temporality, and as such it makes possible the Constitution of the structure of care.
Heidegger's conception seems to be that it is because we are fundamentally temporal - having the formal structure of ecstatic-horizontals unity - that we can project, authentically or inauthentically, our concernful dealings in the world and exist as Being-in-the-world. It is on this account that temporality is said to found spatiality.
Since Heidegger uses the term "temporality" rather than "an authentic temporality" whenever the founding relation is discussed between space and time, I will begin the following analysis by assuming that it is originary temporality that founds Dasein's spatiality. On this assumption two interpretations of the argument are possible, but both are unsuccessful given his phenomenological framework.
The principal argument, entitled "The Temporality of the Spatiality that is Characteristic of Dasein." Heidegger begins the section with the following remark: Though the expression `temporality' does not signify what one understands by "time" when one talks about `space and time', nevertheless spatiality seems to make up another basic attribute of Dasein corresponding to temporality. Thus with Dasein's spatiality, existential-temporal analysis seems to come to a limit, so that this entity that we call "Dasein," must be considered as `temporal' `and' as spatial coordinately.
Accordingly, Heidegger asks, "Has our existential-temporal analysis of Dasein thus been brought to a halt . . . by the spatiality that is characteristic of Dasein . . . and Being-in-the-world?" His answer is no. He argues that since "Dasein's constitution and its ways to be are possible ontologically only on the basis of temporality," and since the "spatiality that is characteristic of Dasein . . . belongs to Being-in-the-world," it follows that "Dasein's specific spatiality must be grounded in temporality."
Heidegger's claim is that the totality of regions-de-severance-directionality can be organized and re-organized, "because Dasein as temporality is ecstatic-horizontals in its Being." Because Dasein exists futurely as "for-the-sake-of-which," it can discover regions. Thus, Heidegger remarks: "Only on the basis of its ecstatic-horizontals temporality is it possible for Dasein to break into space."
However, in order to establish that temporality founds spatiality, Heidegger would have to show that spatiality and temporality must be distinguished in such a way that temporality not only shares a content with spatiality but also has additional content as well. In other words, they must be truly distinct and not just analytically distinguishable. But what is the content of "the ecstatic-horizontals constitution of temporality?" Does it have a content above and beyond Being-in-the-world? Nicholson poses the same question as follows: Is it human care that accounts for the characteristic features of a humanistic temporality? Or is it, as Heidegger says, human temporality that accounts for the characteristic features of human care, serves as their foundation? The first alternative, according to Nicholson, is to reduce temporality to care: "the specific attributes of the temporality of Dasein . . . would be in their roots not aspects of temporality but reflections of Dasein's care." The second alternative is to treat temporality as having some content above and beyond care: "the three-fold constitution of care stems from the three-fold constitution of temporality."
Nicholson argues that the second alternative is the correct reading.18 Dasein lives in the world by making choices, but "the ecstasies of temporality lies well prior to any choice . . . so our study of care introduces us to a matter whose scope outreaches care: the ecstasies of temporality itself." Accordingly, "What was able to make clear is that the reign of temporal ecstasies over the choices we make accords with the place we occupy as finite beings in the world."
But if Nicholson's interpretation is right, what would be the content of "the ecstasies of the temporality itself," if not some sort of purely formal entity or condition such as Kant's "pure intuition?" But this would imply that Heidegger has left phenomenology behind and is now engaging in establishing a transcendental framework outside the analysis of Being-in-the-world, such that this formal structure founds Being-in-the-world. This is inconsistent with his initial claim that Being-in-the-world is itself foundational.
Nicholson's first alternative offers a more consistent reading. The structure of temporality should be treated as an abstraction from Dasein's Being-in-the-world, specifically from care. In this case, the content of temporality is just the past and the present and the future ways of Being-in-the-world. Heidegger's own words support this reading: "as Dasein temporalizes itself, a world is too," and "the world is neither present-at-hand nor ready-to-hand, but temporalizes itself in temporality." He also states that the zuhanden "world-time, in the rigorous sense of the existential-temporal conception of the world, belongs as itself." In this reading, "temporality temporalizing itself," "Dasein's projection," and "the temporal projections of the world" are three different ways of describing the same "happening" of Being-in-the-world, which Heidegger calls "self-directive."
However, if this is the case, then temporality does not found spatiality, except perhaps in the trivial sense that spatiality is built into the notion of care that is identified with temporality. The fulfilling contents of “temporality temporalizing itself” simply is the various openings of regions, i.e., Dasein's "breaking into space." Certainly, as Stroeker points out, it is true that "nearness and remoteness are spatially-transient phenomena and cannot be conceived without a temporal moment." But this necessity does not constitute a foundation. Rather, they are equiprimordial. The addition of temporal dimensions does indeed complete the discussion of spatiality, which abstracted from time. But this completion, while it better articulates the whole of Being-in-the-world, does not show that temporality is more fundamental.
If temporality and spatiality are equiprimordial, then all of the supposedly founding relations between temporality and spatiality could just as well be reversed and still hold true. Heidegger's view is that "because Dasein as temporality is ecstatic-horizontals in its Being, it can take along with it a space for which it has made room, and it can do so farcically and constantly." But if Dasein is essentially a factical projection, then the reverse should also be true. Heidegger appears to have assumed the priority of temporality over spatiality perhaps under the influence of Kant, Husserl, or Dilthey, and then based his analyses on that assumption.
However, there may still be a way to save Heidegger's foundational project in terms of authentic temporality. Heidegger never specifically mentions the authenticity of temporalities, since he suggests earlier that the primary manifestation of temporality is authentic temporality, such a reading may perhaps be justified. This reading would treat the whole spatio-temporal structure of Being-in-the-world. The resoluteness of authentic temporality, arising out of Dasein's own "Being-towards-death," would supply a content to temporality above and beyond everyday involvements.
Heidegger is said to have its foundations in resoluteness, Dasein determines its own Situation through anticipatory resoluteness, which includes particular locations and involvements, i.e., the spatiality of Being-in-the-world. The same set of circumstances could be transformed into a new situation with different significance, if Dasein chooses resolutely to bring that about. Authentic temporality in this case can be said to found spatiality, since Dasein's spatiality is determined by resoluteness. This reading moreover enables Heidegger to construct a hierarchical relation between temporality and spatiality within Being-in-the-world than going outside of it to a formal transcendental principle, since the choice of spatiality is grasped phenomenological ly in terms of the concrete experience of decision.
Moreover, one might argue that according to Heidegger one's own grasp of "death" is uniquely a temporal mode of existence, whereas there is no such weighty conception involving spatiality. Death is what makes Dasein "stands before itself in its own most potentiality-for-Being." Authentic Being-towards-death is a "Being towards a possibility - indeed, towards a distinctive possibility of Dasein itself." One could argue that notions such as "potentiality" and "possibility" are distinctively temporal, nonspatial notions. So "Being-towards-death," as temporal, appears to be much more ontologically "fundamental" than spatiality.
However, Heidegger is not yet out of the woods. I believe that labelling the notions of anticipatory resoluteness, Being-towards-death, potentiality, and possibility specifically as temporal modes of being (to the exclusion of spatiality) begs the question. Given Heidegger's phenomenological framework, why assume that these notions are only temporal (without spatial dimensions)? If Being-towards-death, potentiality-for-Being, and possibilities were "purely" temporal notions, what phenomenological sense can we make of such abstract conceptions, given that these are manifestly our modes of existence as bodily beings? Heidegger cannot have in mind such an abstract notion of time, if he wants to treat of the proposed authenticity that corragulates of temporality is the meaning of care. It would seem more consistent with his theoretical framework to say that Being-towards-death is a rich spatio-temporal mode of being, given that Dasein is Being-in-the-world.
Furthermore, the interpretation that defines resoluteness as uniquely temporal suggests too much of a voluntaristic or subjectivistic notion of the self that controls its own Being-in-the-world from the standpoint of its future. This would drive a wedge between the self and its Being-in-the-world, thereby creating a temporal "inner self" which can decide its own spatiality. However, if Dasein is Being-in-the-world as Heidegger claims, then all of Dasein's decisions should be viewed as concretely grounded in Being-in-the-world. If so, spatiality must be an essential constitutive element.
Hence, authentic temporality, if construed narrowly as the mode of temporality, at first appears to be able to found spatiality, but it also commits Heidegger either to an account of time that is too abstract, or to the notion of the self far more like Sartre's than his own. What is lacking in Heidegger's theory that generates this sort of difficulty is a developed conception of Dasein as a lived body - a notion more fully developed by Merleau-Ponty.
The elements of a more consistent interpretation of authentic temporality are present in Being and Time. This interpretation incorporates a view of "authentic spatiality" in the notion of authentic temporality. This would be Dasein's resolutely grasping its own spatio-temporal finitude with respect to its place and its world. Dasein is born at a particular place, lives in a particular place, dies in a particular place, all of which it can relate to in an authentic way. The place Dasein lives are not a place of anonymous involvements. The place of Dasein must be there where its own potentiality-for-Being is realized. Dasein's place is thus a determination of its existence. Had Heidegger developed such a conception more fully, he would have seen that temporality is equiprimordial with thoroughly spatial and contextual Being-in-the-world. They are distinguishable but equally fundamental ways of emphasizing our finitude.
The internalized tensions within his theory eventually led Heidegger to reconsider his own positions. In his later period, he explicitly develops what may be viewed as a conception of authentic spatiality. For instance, in "Building Dwelling Thinking," Heidegger states that Dasein's relations to locations and to spaces inheres in dwelling, and dwelling is the basic character of our Being. The notion of dwelling expresses an affirmation of spatial finitude. Through this affirmation one acquires a proper relation to one's environment.
But the idea of dwelling must accede to the fact that has already been discussed in Being and Time, regarding the term "Being-in-the-world," Heidegger explains that the word "in" is derived from "in-an" - to "reside," "habits are," "to dwell." The emphasis on "dwelling" highlights the essentially "worldly" character of the self.
Thus from the beginning Heidegger had a conception of spatial finitude, but this fundamental insight was undeveloped because of his ambition to carry out the foundational project that favoured time. From the 1930's on, as Heidegger abandons the foundational project focussing on temporality, the conception of authentic spatiality comes to the fore. For example, in Discourse on Thinking Heidegger considers the spatial character of Being as "that-which-regions (die Gegnet)." The peculiar expression is a re-conceptualization of the notion of "region" as it appeared in Being and Time. Region is given an active character and defined as the "openness that surrounds us" which "comes to meet us." By giving it an active character, Heidegger wants to emphasize that region is not brought into being by us, but rather exists in its own right, as that which expresses our spatial existence. Heidegger states that "one needs to understand ‘resolve’ (Entschlossenheit) as it is understood in Being and Time: as the opening of man [Dasein] particularly undertaken by him for openness, . . . which we think of as that-which-regions." Here Heidegger is asserting an authentic conception of spatiality. The finitude expressed in the notion of Being-in-the-world is thus transformed into an authentic recognition of our finite worldly existence in later writings.
Meanwhile, it seems that it is nonetheless, natural to combine this close connection with conclusions by proposing an account of self-consciousness, as to the capacity to think “I”-thoughts that are immune to error through misidentification, though misidentification varies with the semantics of the “self” - this would be a redundant account of self-consciousness. Once we have an account of what it is to be capable of thinking “I”-thoughts, we will have explained everything distinctive about self-consciousness. It stems from the thought that what is distinctive about “I”-thoughts are that they are either themselves immune to error or they rest on further “I” -Thoughts that are immune in that way.
Once we have an account of what it is to be capable of thinking thoughts that are immune to error through misidentification, we will have explained everything about the capacity to think “I”-thoughts. As it would to claim of deriving from the thought that immunity to error through misidentification depends on the semantics of the “self.”
Once, again, that when we have an account of the semantics in that we will have explained everything distinctive about the capacity to think thoughts that are immune to error through misidentification.
The suggestion is that the semantics of “self-ness” will explain what is distinctive about the capacity to think thoughts immune to error through misidentification. Semantics alone cannot be expected to explain the capacity for thinking thoughts. The point in fact, that all that there is to the capacity of think thoughts that are immune tp error is the capacity to think the sort of thought whose natural linguistic expression involves the “self,” where this capacity is given by mastery of the semantics of “self-ness.” Yielding, to explain what it is to master the semantics of “self-ness,” especially to think thoughts immune to error through misidentification.
On this view, the mastery of the semantics of “self-ness” may be construed as for the single most important explanation in a theory of “self-consciousness.”
Its quickened reformulation might be put to a defender of “redundancy” or the deflationary theory is how mastery of the semantics of “self-ness” can make sense of the distinction between “self-ness contents” that are immune to error through misidentification and the “self contents” that lack such immunity. However, this is only an apparent difficulty when one remembers that those of the “selves” content is immune to error through misidentification, because, those employing ‘”I” as object, were able in having to break down their component elements. The identification component and the predication components that for which if the composite identification components of each are of such judgements that mastery of the semantics of “self-regulatory” content must be called upon to explain. Identification component are, of course, immune to error through misidentification.
It is also important to stress how the redundancy and the deflationary theory of self-consciousness, and any theory of self-consciousness that accords a serious role in self-consciousness to mastery of the semantics of the “self-ness,” are motivated by an important principle that has governed much of the development of analytical philosophy. The principle is the principle that the analysis of thought can only continue thought, the philosophical analysis of language such that we communicate thoughts by means of language because we have an implicit understanding of the workings of language, that is, of the principle governing the use of language: It is these principles, which relate to what is open to view and mind other that via the medium of language, which endow our sentences with the senses that they carry. In order to analyse thought, therefore, it is necessary to make explicitly those principles, regulating our use of language, which we already implicitly grasp.
Still, at the core of the notion of broad self-consciousness is the recognition of what consciousness is the recognition of what developmental psychologist’s call “self-world dualism.” Any subject properly described as self-conscious must be able to register the distinction between himself and the world, of course, this is a distinction that can be registered in a variety of way. The capacity for self-ascription of thoughts and experiences, in combination with the capacity to understand the world as a spatial and causally structured system of mind-independent objects, is a high-level way of registering of this distinction.
Consciousness of objects is closely related to sentience and to being awake. It is (at least) being in somewhat of a distinct informational and behavioural intention where its responsive state is for one's condition as played within the immediateness of environmental surroundings. It is the ability, for example, to process and act responsively to information about food, friends, foes, and other items of relevance. One finds consciousness of objects in creatures much less complex than human beings. It is what we (at any rate first and primarily) have in mind when we say of some person or animal as it is coming out of general anaesthesia, ‘It is regaining consciousness’ as consciousness of objects is not just any form of informational access to the world, but the knowing about and being conscious of, things in the world.
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